After several days of wondering, if i was the only person for whom forum does not work correcty anymore, if finally found the problem...
I must have chosen german as the prefered language some days ago...
What happened was, that all the button-texts were gone and there was a note about some copyright-problems...
To the Forum-Admin, please check the languages and either deactivate German or install it properly... I guess, some people might be irritated and not come back, if they're only looking for tech-support and not even the forum works...
By the way, who is the forum-admin and is there one at all ?
Best regards,
Chewi