He asked me if I had visited the UK before.

?
He asked why I wanted to study Italian.

?
He asked me if I had studied German at school.
He asked me if I was Italian.

?

?
He asked me how long I was going to stay in the US.

?
He asked me what my surname was.

?

1.Did you visited UK before?

2. Why do you want to study Italian?

3. Did you study German at school?

4. Are you Italian?

5. How long are you going to stay in the US?

6. What is your surname?

Можешь добавить в начале he ask/ed,'''' или в конце '''-he ask/ed, но это не обязательно.