Your subject heading also makes no sense. Only you can edit your post to change it to something meaningful.

It works fine for me. Can you give us more details about what you’re trying to do, and what you’re doing?

>The tempo marking which I set only lasts for one bar. Why is that? It must be fixed now! Thnere used to be a tempo tool, now it only exists as an expression tool. This makes no sense<

Without more information, no one can help you. I have no problem setting tempo per the Help files.