Yukarı mı literally jeans “is it to up” but it's a shortened version of “Yukarı mı çıkıyorsun?“ “are you going up” and going down would be aşağıya inmek, in fact both of these sentences have grammatical errors since in Turkish inmek is only used for down and çıkmak is only used for up and above but in daily language it's always used like that. And um other things that could be helpful are those “Sen nereye gidiyorsun/ Siz nereye gidiyorsunuz?” (Where are you young?), “Hangi katta oturuyorsun/oturuyorsunuz?” “On which floor do you live?” these are building conversation context I can think of, don't hesitate to ask the translation of any sentence, good luck!

If he/she asks you to " Yukarı mı? (are you going up?)" You could answer "Evet, yukarı(yes, going up)" or "Evet, aşağıya(Yes, going down)". Basically going up can be translated "yukarı", going down is "aşağı"