Are these sentences are correct?
Please inform me which sentences are correct.
Is it not saving time?
or
Isn't it saving time?
Isn't it a way to correct our mistakes?
or
Is it not a way to correct our mistakes?
Wasn't it is a way to correct our mistakes?
or
Was it not a way to correct our mistakes?
Doen't it help them to learn something?
or
Does it not help them to learn something?