"We are not buying a house yet."
Translation:Henüz bir ev almıyoruz.
You can always put 'henüz' before the noun(Of course, if the noun is in a adjective compound henüz comes before it,too.). But to put it between noun and verb there is a rule: The noun should be in accusative case. Because 'ev almak' states a phrase together so you can not seperate it. I am not sure but 'ev almıyoruz' is the predicate here and not 'almıyoruz'.