suggest reasons (in terms of language learning difficulties)

The following sentenses contains errors. I managed to correct the errors, but i'm not sure how to explain how and why they could have been made. Please can you help me? They are as follows:-

1. My brother is more older than me. > My brother is older than me.

2. He is now 20 year old. He live in Taiwan. > He is now 20 years old. He lives in Taiwan.

3. He studies to be a electrical engineer. > He studies to be an electrical engineer.

4. He is funny and he have got a beautiful girlfriend. > He is funny and have a beautiful girlfriend.

5. She is also wanting to be an engineer. > She also wants to be an engineer

6. Last year he has gone to America to study English for one month. > He went to America for one month last year to study English.

7. My father borrowed him a suitcase to carry his things. > My father lent him a suitcase to carry his things.

8. He buyed much things when he is there. > He bought many things when he was there.

9. Now I am study in America and he is in China again. > Now I am studying in America and he is China again.