Possessive determiner reference

I was writing something, then I came across something confusing. I googled but I can't find what I need to know. I'm trying to learn grammar.

In third person writing, there's subject, object, and possessive. But if there's more than a two nouns, and these two possesses their own object, how do I point out which of their possession with the pronouns?

Ah, sorry I'm bad at explaining, I don't even know what am I saying, so here's an example. Mr. A and Mr. B each has their own table. Mr. B is pushing Mr. A away from Mr. A's desk.

Here's the sentence;
"Mr. A said as he struggled to stop Mr. B from pushing him away from his desk."

Here are my questions from the sentence above;
Is "He" refers to Mr. A?
Is "Him" refers to Mr. A?
Is "His" refers to Mr. A's desk?

Thanks!