"Why are you waiting here?"
Translation:Burada neden bekliyorsun?
Burası = This place. ; Burada = In this place.
Why are you waiting here = Why are you waiting in this place
So you need "burada".
Subject-Object-Verb. Question words go where the answer would go in the sentence. There is a lot of flexibility as to where adverbs go normally as well. The most stressed item comes direct before the verb if you want to change the word order for stress.
could i say like 'burada ne (or neyi) bekliyorsun?' why 'neden' is used here?
"neyi bekliyorsun" would be "What are you waiting for"
"neden" means "why"
present continuous tense suffix is always -iyor/-ıyor/-uyor/-üyor and any additional suffix will use "u," per the notes and tips section, with the exception of plural human actions which may use the additional suffix -lar. We are paying? Ödüyoruz. Y'all are coming = Geliyorsunuz. They (humans) are writing = Yazıyorlar