Sorry, I don't know enough in Polish to help out directly. Hopefully someone else can put this into Polish. But in the USA if someone said "What do you think you are doing" it is because you are doing something they question or dislike. For example -- if someone goes ahead of you in a queue/line at the store (sklep), you might say "Hey, what do you think you are doing?" Many times it is used expletively, e.g.: What the heck/hell do you think you are doing?