I learn English from Friends series, am at the second episode of first season. I don't know how to define sentence: "like i wasn't dreading tomorrow enough having to give it back to him" and second sentence: "as far as my parents are concerned" -> can I define it like: "according to my parents"?
The TV show Friends has been popular enough that it's possible to find descriptions of the episodes on Wikipedia. I have not seen the episode and am extrapolating some of my answer.
If you post more questions like this one, you should include who makes the statement, the full statement, not just a phrase, and if possible, the statements that come before and after. All this information provides context and makes it easier for others to explain the colloquial and often slangy conversations.
"like I wasn't dreading tomorrow enough having to give it back to him"
Rachel plans to return an engagement ring to Barry. She's calling off their engagement to be married.
"having to give it back to him" is returning the ring and Barry is probably not going to take it well.
"like I wasn't dreading tomorrow enough" is more complicated. Let's make it a positive statement: "I am dreading tomorrow"
Rachel is unhappy or worried about returning the ring because Barry will be upset.
Making the statement negative and adding "like...enough" implies that something beyond the next statement ("having to give it back to him") has occurred. Maybe Barry called and said how he was looking forward to their meeting or is already making wedding plans. So Rachel is now doubly worried and upset about what may happen tomorrow.
The Wikipedia article reveals that Monica and Ross (siblings) have a meal with their parents, one of them makes the statement including "as far as my parents are concerned".
While, normally, "according to my parents" could be considered an equivalent statement, knowing the show, "as far as my parents are concerned" implies that the parents are ignorant of something (Ross is going to be a baby daddy?) or that the speaker disagrees with an opinion held by the parents. This is very speculative because we really need the full sentence.