Impressum (contact address)
germany Anonymitiy does not excuse not complying with § 5 DDG (formerly: TMG)
The DDG - digital services law, formerly known as TMG, TeleMedia Law - prescribes in §5, that as soon as you offer any service in commerce, then you have to always provide an "Impressum", which needs to contain a physical address where lawsuits can be delivered, and the name of who is responsible for the site. This Impressum has to be both easily accessible, and easily recognizable. As such, German domains (or domains of German Companies) usually have a link labeled as Impressum or contact at the bottom or in the menu.
A site being private does not change the fact that it is commercial or not: an access-restricted bar is private in that it is not open to the public, but it is commercial. A playground might be private (=access restricted) or public, and still isn't commercial unless you charge access fees.
The only light at the end of the tunnel here? The DDG applies to digital services of natural or legal persons that have their seat in Germany. The domain ending is irrelevant, the seat of the owner is.
Also, §5 only applies to commercial services. As a simple example, a mere photo album would not be commercial unless you charge for access or offer your services to create or sell the items depicted. However, the line between commercial and not can be complicated: as soon as anything is offered for any sort of compensation, you could be considered commercial. While a discussion forum or blog about how to fix your bike is inherently non-commercial, the presence of advertisements, a Patreon, sponsored content, or sponsored links to products could change that nature to commercial. At which point of ads that would be the case would be determined by the Staatsanwaltschaft (state attorney offices), and is out of scope for here.
Slight side note: you do not need to register your digital service anywhere, or gain a license for it, under §4 DDG.
The DDG calls out 2000/31/EG and 2010/13/EU, as well as 2019/1150, as it establishes its boundaries, applicability and jurisdiction in §1 to §3 DDG. These three matters of European legislation (though of different bodies) all indicate that very similar rules are in place all over the EU and EG. It also points to numerous other European legislations all over, and how it implements those. As a result, you most likely are obligated to have a legal address publicly posted on your website under which you are reachable as soon as you engage in any sort of commerce.
The caveat here is, that you need to be operating out of the EU. Should you operate out of for example sudan, then these laws don't apply, but Sudanese law would. And... according to CIPESA, you don't really want to operate under Sudanese internet law.
Cookie Policy
As long as you don't create cookies, no law obligates you to have a cookie policy.
As soon as you do set cookies, you need a cookie policy under GDPR and e-privacy Directive. For some cookies consent isn't necessary, but you still need a policy explaining them.