1) I used these shoes roughly; they should have been torn by now.
2) At that speed, I thought he would kill them!
3) >>Your sentence was perfect!
4) No one knows what their future is. (Or: No one knows what their future will be.)
5) How much does it cost after the discount?
6) >>I could not understand the meaning of your original sentence well enough to correct it.
7) Everybody has the right to live in the way they like.
8) From his speech, I thought he was the manager.
9) I thought they might have arrived before now.
10) They might have been married.