Hi,

If there’s something that ya want, just keep on pushing for ‘em.
-This means “…If you really want to obtain or achieve something, just keep on trying and struggling for success.”?

2.Now what ya wanna do, I will leave that up to you.
-This means “……………….., I will leave that to you so you can do whatever you like”, right?I'll let you decide what you want to do.

3.My boss is cheating on his wife, and this is really eating at me.
-What does “this is really eating at me” mean here? It's bothering me a lot, causing me a lot of mental anguish and unhappiness.

4.He has been screwed over by every girl he’s liked.
-“Screwed over” here means “to be cheated on”, right? Perhaps, but necessarily. Could just be that they caused him a lot of trouble, treated him badly and unfairly.

5.If you begin to act needy, it will be a turnoff to him.
-What does “turnoff” mean here? It will destroy his positive feelings for you. It will make him dislike you.

6.A: Those mean “ we will love each other forever”, right man?
B: Simply put, yes!

-What does “simply put” mean here? Without going into details. I'll just give you a simple answer. It's not a phrase that would be used by people talking in this level of informal English.

Best wishes, Clive