When I connect to the server, it takes me out after a while and tells me connection lost. If I press "o", it appears, you can not have any origin. I already tried single player and it works.

I am the only one among my friends who cannot enter the server

My friend was able to manually add the origin to me but after 2 minutes I was disconnected from the server and the origin was removed again.

This sounds like your connection to the server is very bad. Try running it in the same configuration on a local server to see if the problem still persists.