Future tenses

Hello! Can you help me please? I need to correct the mistakes in sentences. I did it. But I'm not sure that i've done it right. Someone check it please. I'm not good at English so if I already have done mistakes in my sentences it'll be good if you correct it too.

1.Many scientists believe it's impossible that one day we live on other planets.
2.This time tomorrow i'll write an email.
3.I don't believe that computers will ever developed to be more intelligent than humans.
4.I'll finish fixing this computer by the time my boss comes back.
5.In thirty years' time , most people will have used their TV as the screen for their computers.
6.By the time he finisher his computer course , he'll be spending over 500 dollars.

1.Many scientists believe it's impossible that one day we will live on other planets.

2.This time tomorrow i'll be writing an email.

3.I don't believe that computers will ever be developed to be more intelligent than humans.

4.I'll have finished fixing this computer by the time my boss comes back.

5.In thirty years' time , most people will be using/will use their TV as the screen for their computers.

6.By the time he finishes his computer course , he'll have spent over 500 dollars.