I am currently a student at a school with a fairly low english level. I live in a non-english country. I am bringing this up not becuase it really changes anything, but rather to clarify that the English we are learning should not really be judged on a university level. I understand that if I was a Cambridge English master student, this would of course be pointed out. But since this is far from the truth, here is my question if (a) the useage of commas in those examples is correct, and (b), how necessary are they. Do they integral to the understanding of the written text or are they only used in the most official context since no one bothers to put them there.
Anyway, the sentences are:
Yesterday, I ate a grilled cheese sandwich.
For months, I hated cheese.
Luckily, I had my grilled cheese sandwich.
Every day, I eat my grilled cheese sandwich now.
Now, I know that commas used before things but infront of the subject are common, as seen with the 'Anyway, the sentences are:' and 'Now, I know...'. But in the examples above it just seems out of place. I really value good English and proper grammar, so I am asking you, that, if this is actually how you are supposed to do this, how bad is it to just not do it in most contexts, such as official Email and letters? Will people read that I missed the ',' and will they instantly see me as this babric creature or will they not even notice? Should I also pause after injections when talking?