the bonus mission - Trap (or somthing)
 

this is impossible, i tried moving directly to the selfpropeled gun, even if i do take it the slugger or what ever its called blows it up with one shot.

i usuall unable to get it or free the POW befor alot of allied tanks come and kill my guys

Any tips how to approch this?
it is unbelivbly hard

this is how i did it:

move your soldiers to where the german assault tank is but dont get in yet. then start killing everyone whos around. this may take a while. just let one half of the soldiers cover the left, the other one the right flank. once theres no threat, send one guy to repair the tanks track. when finished move your tank CAREFULLY and try to take out the american tank - that has been on the map from the beginning - with one shot. after that move your tank back again and aim at the bridge. when the tanks start rolling in you can easily take them out with one shot. after you killed off the tanks you can go an rescue the POWs. dont forget to arm them since they - of course - have been disarmed. use the tank to shoot down buildings with remaining FOWs. and always keep the officer safe, since he must not die and has to read the papers (which are right in the smal house next to the pows).