Brake frozen HELP!!

Hello finally it’s cold in Germany then something like this….my hand brake (stupidly attracted by my roommate) is frozen, I then drove off, seemed to go well. But now he cracks off and on while driving and the brake pedal can sometimes be passed quite far (like for example with the hand brake tightened) and sometimes it reacts normally. Sometimes he cracks also while braking. Besides, it seems to me that I can pull the hand brake now further than before. Has j demand a competent answer for me?? Mazda 323 1,5l E5 BW, front disc brakes, rear drum (frozen!!) ;-)= Matthias