There was an option at the previous forum, that you could change your nickname and how will it appear at posts/threads, but i cant find it now. If is it removed, can you re-add it please?

Users can not change their usernames in this forum software, you'll have to request a username change here: https://sampforum.blast.hk/showthread.php?tid=157042

The administrators would need to find an addon for vBulletin for that type of thing.