File options, project settings, language pairs etc.

Sometimes I get strange messages when I am working because I don't have languages for a project, and sometimes changes I make to settings that should make Trados behave differently don't affect anything.

I think it is related to the way Trados is very complex with special ways to create projects and work.

I would like to have clear and understandable guidance on how to work properly with Trados to not get these problems.