"I learn from him."
Translation:אני לומד ממנו.
To say "from us", do you say "מאיתנו"? Also to say "from me", do you say "מי"?
When you're talking about anything that is not - me, you, her, he, we.
"אני לומד מהספר"
Yes. And it is very similar for ל = "for"/"to" לי, לך, לו, לנו, להם, להן ל-anything else
If it's something that's specific, you would name that thing: אני לומד מהספר — I learn from the book.
If it was already established that you were talking about the book, you could simply say: אני לומד ממנו — I learn from it/him.
Is מֵאִתַנוּ much more common than מִמֶּנּוּ?
I suppose it's easier to distinguish it 3rd person singular masc from the 1st person plural.
Is he saying: מִמֶּנוֹ ???
Although, the first pronunciation is cited as a colloquial variant in wiktionary.