Don't worry, nothing is easy in the beginning and yes, some docs are not up to date because Lemmy has such a steep development curve and therefore frequent changes.

[...] i think i might try to do it again tomorrow after the frustration of failure of today is gone and i have some more motivation.

Do have any other self hosting experience? Maybe a software that is a bit more easy to handle would be a good starter. With that, you can experiment and learn a bit, before starting a (long term) project that requires proxy, database, frontend, backend and configs to make them work together. Not to speak from the maintenance.

Is it okay if i just ask my questions to you directly in this thread?

Sure thing. I can recommend the Lemmy admin matrix chat as well (if you're a matrix user).

Do you mean DynDNS with the automatic updates?

What I mean is: best case is your provider offers an api which allows you to update the DNS records by running a simple script. What I would not recommend is using something like mylemmy.dyndns.org (or similar services) for a Lemmy instance.