[U4] Use of English1

It's impossible that you saw John last night - he's in the USA!
John's in the USA so you can't have seen him last night.

Modals – deductions about the past (B1/B2)
https://learnenglish.britishcouncil.org/grammar/b1-b2-grammar/modals-deductions-about-the-past

must have + pp: feel sure
might have / may have + pp: it's possible
can't have / couldn't have + pp: it's not possible

I am confident that he will be successful in his career.
I am confident of his chances of success in his career.

If you feel stressed, breathing slowly should calm you down.
Breathing slowly should make you calmer, if you feel stressed.

I am really bad at remembering people's names when I meet them.
I have a bad memory for people's name when I meet them.

He lost his job because he was inefficient.
He lost his job on the grounds of his inefficiency.

I'm sorry that I didn't help him.
I regret not helping him.