Ответ:

He doesn't sell his old things . Does he sell hi old things? She didn't forked out money for this bag . Did she fork out money for this bag ?

Ответ:

1 He doesn't sell his old things.

 Does he sell his own things?

2 She didn't fork out money for this bag.  

  Did she fork the money out for this bag?

3  He isn't checking out prices online now (не уверена)

   Is he checking the prices out online now?

4. He wasn't saving a lot.

   Was he saving a lot?

5. He hasn't just borrowed my book.

   Has he just borrowed my book?