Domains always have to be administered and "rented" by any provider. However, the purchase/sale of a domain is possible via private contracts or sales platforms such as Sedo. This does not replace the regular registration fees for a domain.

If you are interested in a domain which is already registered, you have the possibility to contact the domain holder directly. In order to find the domain holder, you can consult the domain holder in public Whois queries.

https://www.denic.de/ (.DE Domains)

http://whois.icann.org/en (e.g. .COM/.NET/.ORG/.nTLDs)

As a rule, the respective domain holder can be contacted by post or e-mail. For certain domain extensions, it is unfortunately not possible to determine the domain holder (e.g. for .to/.ae domains). Only the name servers are issued there.

In case you cannot find the owner, you can write to the responsible provider (Tech-C),
with the request to forward your request to the domain holder.