Find the mistakes in each of the following sentences :
1-What did you do since last Friday?
2-When would you start to learn English? – Two years ago.
3-I want to be a doctor since I was ten.
4-When I was eight. I have gone to London .
5-We were watching the match when suddenly all the lights were going out.
6-At the moment my sister trains to be a primary teacher.
7-She does research on plants a few years ago.
9-I knew him for ten years.