Dear Teachers,

1. I don't think I can take another heartbreak.

- "take" here means "stand", right? "heart-break" is the pain which is caused when two people break up, right?

2. Is "fall in love with someone" the same meaning as "love someone"?

3. Don't let him get better of you.

- This means "don't let him take advantage of you", right?

4. Is "first off" the same meaning as "first thing first"?

Thanks very much to Teachers,

1. Yes to both.

2. no - it is the process when you realise that you are starting to love someone, the way your feelings are developing at the very start of the relationship. If you love someone you may have loved them for 50 years. You only fall in love with them at the start.

3.yes, or don't let him beat you at something.

4. Without context this is a tricky one, but it usually just means 'Firstly, blah blah blah'.

get the better of
    Also, get the best of; have the better or best of. Become superior to or master someone or something; win out. For example, John's common sense got the better of his pride, and he apologized, or Her older sister was always trying to get the best of her, or He was determined to have the better of his competitors. [c. 1600] Also see get the drop on .

but it also means in informal contexts:

Don't let someone cheat you
(i.e. better you by being smart)

4. Is "first off" the same meaning as "first thing first"?
I think it's just "First, " in may contexts.
say in
First, I need to say that ...