Here are the corrected sentences:
- I was play football yesterday afternoon. -> I was playing football yesterday afternoon.
- She cooked dinner when I was arriving. -> She was cooking dinner when I was arriving. / She cooked dinner when I arrived.
- They was watching TV when the baby cried. -> They were watching TV when the baby cried.
- We were went to the park yesterday. -> We went to the park yesterday.
- He didn't was reading a book. -> He wasn't reading a book. / He didn't read a book.