下面句子中的错误存在于状语从句或者定语从句

高考英语语法

下面句子中的错误存在于状语从句或者定语从句中，请同学们认真思考后加以改正：

1. He lives in the room its door is newly painted.

2. Young although he was, he was fit for the work.

3. All what I need is to take a good rest.

4. I have a lot of friends, some of them are college students.

6. The knife by which we cut the bread is very sharp.

7. You must watch carefully

everything which the teacher does in class.

8. He talked about the teachers and schools which he had visited.