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I'm a little confused, which tense, Present Perfect or Past simple, should I use in the following examples?

Ex.1
A: Your hair looks nice. ................ (you/have) a haircut? Who ............ (cut) it? ................... (you/go) to the hairdresser?
B: No, a friend of mine .......... (do) it for me.

Ex.2

Is that question correct?
"How many plays has Shakesperare written?"

Ex.3
I did German at school but ............. (forget) most of it.

Ex.4
Is that statement correct?
"My parents have got married in London."

Thanks for help!
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Ex.1

A: Your hair looks nice. .. (you/have) a haircut? Who .. (cut) it? .. (you/go) to the hairdresser?

B: No, a friend of mine .. (do) it for me.

Your hair looks nice. Did you have a haircut? (Or, "Have you had a haircut?") Who cut it? Did you go to the hairdresser? No, a friend of mine cut (or did) it for me.

Example 2 is correct.

3. I did German at school but forgot most of it. (In the U.S., we would most often say, "I took German in school but forgot most of it." You could also say, "I took German in school but have forgotten most of it."

4. My parents got married in London. or, if you mean just recently, you would say, "My parents have gotten married in London."

I know that "got" can be the past participle of get, (and used to be the preferred one) but you don't hear it used in spoken English in the U.S., and you would seldom see it written, either. I'm not sure about Canandian or British usage of "got" as the pp.
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Ex. 1
Your hair ooks nice. Did you have your hair cut? Who cut it? Did you go to the hairdresser?
No, a friend of mine did it for me.

Ex. 2
You can't use the present perfect with Shakespeare because he is not alive anymore and that tense brings you up to the present.

Ex. 3
You don't want to use "did" with a language. You studied German at school but forgot most of it.

Ex. 4
You would say that if they just did it. Otherwise, it wouldn't make sense. My parents got married in London.
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Comments  
Maven is correct...although, How many plays has Shakespeare written is a correct sentence, it isn't correct since we all know Shakespeare is dead.

How many plays did Shakespeare write? That would be the correct usage.

Sorry...when I answered above, I was not focused on that.

As far as using "did" to mean took a course or studied, I have heard that in English movies and TV programs, e.g., "I did maths at school." (In Britain they shorten mathmatics to maths. In the U.S. we shorten it to math.) We don't say that in the U.S., but do commonly say, "I took math at school," meaning took a math course, or took math courses. More formally correct would be "studied," as Maven suggests.
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