There's my opinions.Here are some more sentences which I have written as an exercise on the use of a comma. Please, would you correct my mistakes.
Talking about music, he was playing the guitar, and looking at her attentively. Optional
She was at the crossroads of her life, and did not know which way to take. Optional
He had spent decades building up his business, which the earthquake destroyed in a few seconds.
This example is a non-defining clause - requires a comma.
Some time after that, he
has beenwas almost killed in a car crash, which killed his aunt.
This is an unusual sentence.
This example is also a non-defining clause - requires a comma. Note: if you had written "in the car crash which killed his Aunt", that would be a defining clause - no comma.
The plane was first flying high, then, suddenly, probably because of the problem with its engine, it plummeted towards the ground.
Yes, this is correct.
I read the paper, and my friend who is one year older than I
,was reading the book.
No second comma here between the subject and the verb.
Student or Learner