What is the correct pronunciation of 'zijn'? Is it a 'z-' or a 'zh-' sound? In previous lessons it was always 'z-' but now I distinctly hear 'zh-'
In English, there is a very limited way in which the present perfect would work here ("We have stayed there for three months.").
By using "there," you indicate that you are no longer there. The three-month visit must have occurred entirely in the past (or you'd still be "there," and would refer to it as "here").
Because the three-month visit occurred entirely in the past, the most straightforward verb tense would be the simple past: "We stayed there for three months." If, however, you were discussing multiple visits and the duration of each, you could say, "We have stayed there for three months," but it would be more natural to say, "We have stayed there for three months before."
"Typically, when we visit Germany, we stay only a day or two."
"Really? We have stayed there for three months."
Basically, the present perfect sentence in English requires a pretzel of a context. It would be very unusual.
I believe that 'have stayed' is not applicable here, because it would imply that you have stayed many times during that period. I.e. have stayed yesterday, have stayed the day before yesterday and so on until you hit 3 months. Because 'have stayed' means a completed action.