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.