I’ve ______ come back from America, so I don’t think I’ll be going there again for a while.

Which of the following sentences is correct?

What's the problem? Just I've told you how to do it!

What's the problem? I've told you how just do it!

What's the problem? I've just told you how to it!

I’ve ______ seen all her old paintings. Do you know if she has painted anything new recently?

Which of the following sentences is incorrect?

I haven't already started living in Madrid, I love it here

I haven't started living in Madrid yet, so I don't know what it will be like

I have just lived in Madrid, and I want to stay here forever