1. You were wasting your time at the football match; I was cleanig the house.
When you were wasting your time at the football match, I was cleanig the house. OK
By reversing those sentences you will sound more resounding: after all you were not very happy to stay home cleaning up the place while he was having a great time somewhere else:
"When (While) I was cleaning the house, you were wasting your time at the football match".
My choice is with Past Continuous Tense to stress the continuation of your hard work and his long lasting leisure time at the game.
2. You have finished your studies. You must decide what to do.
Now that you have finished your studies you must decide what to do. OK
3. She went for long walks. She always got lost
Whenever she went for long walks she always got lost. OK
4. They were sure the information was correct so they presented it to the director.
The minute they were sure the information was correct they presented it to the director. OK
5. He had the operation. He has felt better.
Ever since he had the opertaion he has felt better.
6.Could you let me know the moment the food is ready?
As soon as the food is ready, let me know. OK
7. She always went to her mother when she had a problem.
Whenever she had a problem she always went to her mother. OK