Burning 'Mein Kampf' in front of the enemy = Ridiculous
I am really tired of this anti-Nazi crap in every WW2 movie, be it Hollywood one or European one. No German soldier would have humiliated his leader in front of enemy soldiers. German officers may not like Hitler ( But you should know that popularity of Hitler among the soldiers were very high early in the war ), but burning his book unnecessarily is just *beep* And think like that Josepf liked leader of his country and admired him. You are his friend and you burn his book for no reason. This doesn't make any sense.
That movie is a way overrated and doesn't deserve anything better than 4. Other crap :
+ British soldier asks German officer that why Hitler conquered most of Europe ? This is wrong, at that point, only Poland and Denmark were invaded. Norway was currently being invaded. France and Benelux countries were all around and alive. So, his question is pointless.
+ No prisoner of war could have been as daring as British POWs in the beginning. If you are taken prisoner and act like them in such a situation, you would be shot immediately. There would have been very nervous environment and POWs would probably have been tied.