Unable to answer "What are the opening hours here?" – Diamond Harbour medical centre (Doctor) – way/320487311 via StreetComplete 58.2:

Under construction.

Many buildings in this area are not in the map. Is there a public resource to implement them?

via StreetComplete 58.2

Unable to answer "Who is allowed to park here? Parking may be free or paid." – Parking Lot – way/863243629 via StreetComplete 58.2:

Parking at the roadside of Beach Road is public.
Parking next to the Surf Lifesaving Club is private (Lifeguards only)

Unable to answer "Does this bench have a backrest?" – Bench – node/12179240088 via StreetComplete 58.2:

Teilweise

Attached photo(s):
https://westnordost.de/p/240041.jpg

Unable to answer "Does this bench have a backrest?" – Bench – node/12179280763 via StreetComplete 58.2:

Teilweise

Attached photo(s):
https://westnordost.de/p/240042.jpg

Unable to answer "Do you need to pay to enter here?" – Historic Cape Light museum (Museum) – node/6501457712 via StreetComplete 58.2:

Admission by donation.

Here is a sign, the purpose is historical information

via StreetComplete 58.2

Attached photo(s):
https://westnordost.de/p/232759.jpg

Waimanalo Lagoon Freedom Camping Site
Here is a freedom Campsite for up to 4 self contained vehicles.
There is a wheelchair accessible toilet nearby (see other comment), where there is also a water tap available for campers.
No power is available for campers.

via StreetComplete 58.2

Attached photo(s):
https://westnordost.de/p/232756.jpg

Here is a bench, made from wood

via StreetComplete 58.2

Attached photo(s):
https://westnordost.de/p/232758.jpg

Here is a bench, made from wood.

via StreetComplete 58.2

Attached photo(s):
https://westnordost.de/p/232757.jpg