3 sentences ;)

1) Maybe I would come back to the city the next week if I didn't find him at home.
I have not her sister's phone number.
2) If he hadn't gone from university, he would have been able to go to China.
He was propose the great work here/
3) If you had known everything, why wouldn't you have staied them? It was honest.

Conditionals are very difficult!  I understood your words, but wasn't always sure about the time.  :) Some suggestions for corrections:

1.  Maybe I'll go back to the city next week if he isn't home.  (Future)

2. If he hadn't left university, he would have been able to go to China. He had a great job opportunity there.  (Past)

3. If you knew everything, why didn't you say anything? It would have been the honest thing to do. (Past)