It’s not possible/it can’t be true/I don’t believe that she did...

Why not

It’s not possible/it can’t be true/I don’t believe that she has done

?

A: sorry about you losing your job.
B: How do you know I lost my job?
A: Robert told me yesterday.
B: He can’t/couldn’t have told you yesterday - I only told him this morning.

I mean if we write the full phrase "It can't be true that..." it must be Past Simple -"she did" or Present Perfect - "she has done"?

Yeah, the second part can be anything: will do, has done, did, would do, etc.

Wait, it means

She can't have done

can mean

It can't be true she will do

It can't be true she has done

It can't be true she did

It can't be true she would do

It's a billion variants. It's insanity. It can't be true!xD

No, I’m just kidding. It means “I refuse to believe that she did/has done [something]”

However, "She can have done" is not used becase it's affirmative?

Exactly

But theoretically, if we used it, the full sentence would be like "It can be true that she has done it"?

No, the opposite of “she can’t have done it” is “she must have done it”

But what if I mean "It can be possible that she has done"? So I am not sure 100% that it's true but I dont say it"s impossible, either. This way it would be "She may have done it"?

Yes, sorry, MAY/MIGHT have done it

Sooo,

Exactly not% - She can't have done it = It can't be possible that she has done/did it

Maybe% - She may have done it = it may be possible that she has done/did it

Sure% - She must have done = It must be possible that she has done/did it

This way?

Yes 👍🏼

MUST here means должно быть

Yeah, I know about "Должно быть":)

By the way, "She couldnt have done" = "It couldn't be possible that she had done"

But what about

"She could have done"? Can we write it like

"It could be possible that she had done"?