Since some days, i can only choose contract or extend when i click a joint. How can i fix that?

Try highlighting the joint and clicking the "x" key. That will either hold or relax the joint.

and changing in the options mouse buttons to "1" will fix it completely.

Thank you so much! Now i remember how this came out, i was fooling around in the default.cfg for some reason and Mouse Buttons was set to 3. Now everything works fine again.

Thank Tori-God that he made wise fighters.