It is a common sense that or It is common sense that?

English as a Second Language English Vocabulary, Grammar and Idioms
1

It is a common sense that many people, including your friends, will depart from you on account of many kinds of reasons in your lifetime.

It is common sense that many people, including your friends, will depart from you on account of many kinds of reasons in your lifetime

Which sentence is right?

2

‘It is common sense…’ without the article is correct, but the rest of your sentence needs some work. I suggest:
It is common sense that during your lifetime, many people, including your friends, will part company from you for various reasons.

3

Beeesneees,

  1. He has parted company with his wife.
  2. He has parted company from his wife.
    Are both correct?
4

yes

5

Beeesneees,

  1. He has parted with his wife.
  2. He has parted from his wife.
    Are both correct?
6

Only the second is correct.