Hello.

I will really appreciate some help.
1)Is the preposition "in" OK in the sentence "they had a conversation in which they agreed ..."?
2)Is it possible to say "they met tete-a-tete"? If yes, which order is OK "they met in London tete-a-tete" or "they met tete-a-tete in London"?
3)Is it correct to use "many" in the context: "how many forces will remain in Afghanistan"?
Thank you very much for your help.

1. Yes, as long as you don't repeat "in" unnecessarily later in the sentence.

2. All are fine.

3. Yes, that's correct.