"Mówisz po angielsku."
Translation:You speak English.
Isn't it fascinating how "po angielsku" sounds/feels like speaking "the angels language" =),.. this word was my first impression about Polish and a very strong motivation to try it (besides, I lived in Poland when I was a child, but I was less than 3 years old and I can't rememvber any single word in Polish.. so I have actually been waiting for this course to become available for quite a while already =).
It means either the purpose or reason (why) you are doing something, or the way to do it (in what manner or how you do it), e.g.:
po chleb = in order to get some bread
po angielsku = in english (like in "written in english")
There may be more examples, these are just a few that came to my mind instantly.
I had the same answer as yours. I asked my Polish friends, they told me, if I want to ask "Do you speak English?", it is better to add question mark, or using "Czy mówisz po angielsku?". I don't know why, my friends just told me they do it by feelings :D So, hope my reply would give you a new way to think about it. If you know why in the future, I would like to communicate with you.
difference between statement and question is in question mark/ intonation.
It's better to use "czy" when you are learning because you are struggling with all the other issues and you may not be able to use intonation to imply question. Also "?" questions can sometimes be seen as sarcasm or disbelief, while "czy" questions are more likely seen as genuine questions.