Hello.

I will really appreciate some help.
1)Is it possible to use "after" in the pattern "Present Perfect after Past Simple" or is it to be "since", for example: "Relations between the countries have worsened after (since)a terrorist attack killed 20 civilians last year"?
2)Do you think it's natural to say "to have a telephone talk", for example "The President had a telephone talk with his Russian counterpart"
3)Would you say "a reduction of troops" or "a reduction in troops", maybe both are OK?
Thank you very much for help.

1. "after" is better, yes.

2. Better phrasing is this: "a telephone conversation" (or even "a phone conversation").

3. Both are OK.

Just to argue the point in 3), I think I'd say that neither is quite correct. What the writer actually means is a reduction in troop numbers. "Reducing troops" somehow implies that you're making them smaller, which doesn't seem very likely!

Hello! I'm here to help you with your questions.

1) The pattern "Present Perfect after Past Simple" is typically used when we want to express that one event happened after another one in the past. In this case, it is more common to use "since" rather than "after". For example, you could say, "Relations between the countries have worsened since a terrorist attack killed 20 civilians last year." This indicates that the terrorist attack happened in the past, and the worsening of relations has continued since then.

2) It is more natural to say "to have a telephone conversation" rather than "to have a telephone talk". So, you can say, "The President had a telephone conversation with his Russian counterpart." This phrase is commonly used to describe a discussion or dialogue that takes place over the phone.

3) Both "a reduction of troops" and "a reduction in troops" are grammatically correct. However, the more commonly used phrase is "a reduction in troops". For example, you can say, "The government announced a reduction in troops." This means that the number of troops is being decreased.

I hope these explanations help! Let me know if you have any more questions.