how tight must i set the shrouds beside, is it normal that there is rather a flexible movement in the mast, cause now i feel the mast will fall out when the cat is capsizing.
It is pretty hard to get them too loose. Many racers run them very loose.
The jib halyard tightens everything up, so without the jib the rig should be very loose. With the jib up you can tension the rig any way you want. As a beginner, I would get it fairly tight, but not so much that the mast doesn't rotate freely.