Have you read the OpenStreetMap guidance on mechanical edits (see osm.wiki/Automated_edits)? Also the guidance on good changeset comments is relevant (see osm.wiki/Good_changeset_comments).
Aside from probably contravening the policy on mechanical edits, there are a number of specific issues I've noticed with this changeset. (It seems likely that these issues and other similar issues will be present in other changesets you have made).

1. This changeset does a lot of different things in a number of different locations. The changeset comment does not give any useful explanation for why you are making any of these changes. Even if they could be explained with a single useful changeset comment (which they can't), it would still be useful to split this up into multiple changesets covering a smaller geographic area, so that people view your changesets can get a better understanding of what places are affected by them (unfortunately the main tools for viewing changesets either show just the bounding box, don't work properly for relations, or don't work if the bounding box is too large).
2. You've changed the tagging of 'Killarney Lake' from a reservoir to a lake. It clearly has a dam, so the lake tag may be incorrect (I couldn't find any clear information about what tag is appropriate if an existing lake is enlarged by building a dam, and I have no idea if that scenario is relevant here anyway).
3. You've moved a number of nodes near a fountain by a distance of less than 1m. Why? Also, you've used a fountain=water tag, which is not standard and appears not to have existed anywhere in the world before now.
4. You've been removing a lot of instances of the tag landuse=reservoir, despite this still being a permitted tag. (Mechanical edits that replace one permitted tag with an alternative permitted tag are particularly discouraged. The history of some of the objects you changed in this changeset shows that the change you made here has actually been made before and subsequently reverted).
5. The tag seamark:type=gate seems to just be a duplication of the tag waterway=lock_gate. While both seem to be indepently recommended in the wiki, there seems to be no discussion of why this duplicate tagging is necessary. (This isn't a specific issue for you; rather it's a more general observation that should perhaps be raised elsewhere.)

Can you explain why you have made the changes you made here? For any mistakes you've made, can you please fix them (if possible) and try to avoid making them again in the future?

Thanks,
ACarlotti

I think this tagging is generally better. However, I'm pretty sure there is not a central island on the east side of the roundabout (which is what I understand your tag there to mean). Also, when splitting ways, I think it's generally worth trying to preserve the way history on a sensible part of the way - in this changeset you've instead attached the history of three of the roads to a short stretch of way next to the roundabout. There's nothing I'd do to change it now, but it's something you could consider for future changes.

It looks like you also made some change near the Milton Road/Elizaebth Way roundabout, possibly involving bus route 9, but I can't easily tell what it was. Also, I'm curious as to how this changeset was created by both Potlatch and JOSM.

Reverted in 88828701

I think that improves some things. I've tidied up some further inconsistencies in 88828581; you might be interested in checking what I've done there. Overpass is usually good for viewing the changes in a changeset (though this doesn't show relations) - e.g. https://overpass-api.de/achavi/?changeset=88828581

You also need to remove the construction=residential tags on those roads.

Hello egmont,
It looks like you've included two unrelated sets of changes in this changeset - can you try to ensure that unrelated changes in different parts of the world are uploaded in separate changesets? Looking at your other changesets, I suspect this was just a one-off mistake.

Also, your changeset comments don't say anything useful about what the changeset is doing, which makes it hard for other people (and you in the future) to work out what the intention of the changes was. If you are able to write more descriptive changeset comments in the future, that would be helpful. (This could be in any language - a good comment in a language someone can't read will be more helpful to them than a generic comment in a language they can read). You can read more about good changeset comments on the wiki (osm.wiki/Good_changeset_comments).

I think you've misunderstood how junctions of ways are mapped in OpenStreetMap. According to your changeset, it is no longer possible to get onto taxiway D from taxiway L, or onto the runway from taxiway D, since these ways do not connect (via a shared node). Assuming this is a mistake, can you correct it?
I have a couple more questions in case you have the local knowledge to answer this. According to Esri World Imagery (which I think is the most recent I've seen), the grass to the northeast of taxiway D comes closer to this taxiway than the current mapping shows - is that up-to-date? Also, the same imagery shows runway 10/28 as closed but still in existence - is that the current situation?
Thanks,
ACarlotti

This changeset covers a very large geographic area, which makes it very hard to work out what it actually affects. The changes in Scotland and the changes near Munich should ideally have been in separate changesets (I can't easily tell if you made any changes elsewhere - if so, then it probably should have been more than two changesets).
Also, splitting up changesets that include multiple unrelated sets of changes usually makes it easier to write a useful changeset comment - "various" tells me nothing that I can't already guess from the large size of the changesets bounding box (and that bounding box doesn't tell me much either).

One example is nodes 7773139223 and 7773139227, which lies on the way/58821394. Basically there is no relation between the end of a ditch and a point on the outline of Cambridge - there's no relation between the two, and the presence of one doesn't affect the presence of the other. So we use disjoint features to map them - no shared nodes. On the other hand, if you had a new footpath crossing over a road, then clearly this junction is meaningfully a common point on both objects, so we map it with the same node.

JOSM makes it relatively easy to change objects back to earlier versions (or at least, I know how to do it fairly easily in JOSM). If you want, I can help you fix this (although for the other two boundaries I wouldn't just revert to the previous outlines, because I think they don't make sense in relation to each other). However, it's a minor thing, so I'll leave the data as it is for now to help you learn.

Looking at the Bing imagery, I'd agree that these paths meet at a single point, but I think that point is further north (the path to the east doesn't cross the corner of Charger Green).
Also, as a result of your earlier edit, I think this had the unintended side-effect of changing the outline of the residential area.

Hello mk270, and welcome to OpenStreetMap.
In this changeset you've some of the nodes you've added (for new features) have also been added to existing area boundaries. This is usually incorrect (since the two features merely happen to be in the same place, rather than actually sharing a common point). These node should be detached from the ways you've mistakenly added them to.
This is a common mistake to make, and one I still make sometimes myself. I suggest you try to work out how to avoid adding to the wrong way in your editor, and also have a look at the list of objects your changeset affects before uploading it (I know I can do this in JOSM, but I'm not sure if iD also lets you do that).

Is there pedestrian and cycle access past this closure point? If so, then you need to add a short length of cycleway to connect this up.

Hello Bazzagazza101, and welcome to OpenStreetMap!
I've just been having a look at this changeset, and there several changes within it that look wrong to me. Can you help explain what you've done, so we can work together to resolve any mistakes you've made?
1. Can you clarify what source you used for the population of Bygrave? I notice that you also added a link to the Wikipedia article; Wikipedia is not an allowed source for OpenStreetMap, because the licenses are incompatible (see the warning near the top of osm.wiki/Collaboration_with_Wikipedia for more information). Therefore, if Wikipedia was your source, that part of your change will need to be reverted.
2. You've added a speed limit of 10mph to a road in Stotfold. I'm pretty sure 10mph isn't a legallly enforceable speed limit in the UK, so can you explain why you added this?
3. You've tagged Purbeck Close in Bedford to indicate the pedestrians and horses are banned from using the road. I would be very surprised if pedestrians are banned from what looks like an ordinary residential road.
4. You've tagged the school as "religion=all". This is not a standard use of the religion key; it would be better to have no religion tag.

It would be better to split up changes like this into separate changesets (one for each golf course affected). As it is, the changeset description here implies that you're only changing one golf course, which together with the large changeset bounding box suggests that you could have made some accidental changes elsewhere (though having looked more closely, I don't actually think that was the case here).

Apparently this bridge is not officially open yet (but in practice it is now being used).

I don't know how you reshaped it, but your changeset definitely created a multipolygon where there wasn't a multipolygon before. I've restored this to the original polygon, and deleted the node that was shared with the powerline.
From your description (and other knowledge of the plans), I now think it was fine to delete the future lake.

A few comments.
Firstly, is there any reason you've used a multipolygon to represent the farmland between the two lagoons?
Secondly, you've moved a node onto the powerline. Since powerlines and farmland boundaries don't interact at all, they shouldn't share a node. (Also, moving the node, instead of creating a new one, made it a bit harder for me to understhe history of the field boundary way.)
Finally, if the other lake is planned but not yet built, and has already been mapped, then it would probably be better to use lifecycle prefixes to represent this, instead of deleting the way - e.g change "natural=water,water=lake" to "planned:natural=water,planned:water=lake" (or "contruction:..." if it's already under construction).

I suggest mentioning buses in your changeset comments (e.g. "Update bus route 45a"), so that other people know what you're editing without looking at the contents of the changeset. (I thought it might be building numbers at first).

This changeset also contains a misinterpreation of aerial imagery. The outline you've drawn for the middle building is clearly showing the outline on Bing imagery, which was not taken directly overhead. The actual footprint on the ground is smaller - you've effectively mapped the roof in a different location to the ground floor, and shown it all as a single outline.

Also, I'm pretty sure there is some stuff between this middle building and the large one to the right, though I can't tell what shape it is. (So it could be a building filling the entire gap, or it could just be one or two covered walkways). If you can't tell what it is, then it might be worth adding a note to the map so someone else can fix it later.

I think this is all the feedback I have to offer for now, but feel free to ask me more questions.

I think there are some issues here too. The building to the west of High Street in particular looks as though it has been drawn by tracing around the approximate shape of a roof as viewed from an angle, and different roof heights and shadows might have been misinterpreted.
There are also more example of accidently creating new nodes that are shared by multiple ways when they probably should be.

Also, if you're editing an existing building, it is almost always better retain the original OSM feature, and just edit the tags and move or replace the nodes as needed. This makes it much better to see the history of the building, and identify it as something that was already mapped, rather than something you're mapping for the first time.