Thank you so much.

This is a good way to thank someone who's helped you out. Here are some other situations in which you can say "Thank you so much":

• Your friend let you stay at her house when you were visiting her town for business.
• A coworker agreed to cover your shift.
• A waiter wrapped your leftover food after dinner, so that you could take it home.

(someone) is at (his or her) wits' end

Being "at your wits' end" means that you've tried really hard to solve a problem, but haven't been able to solve it. You say this when you're really frustrated and worried.

I'm at my wits' end with Gabby. She doesn't listen to me, doesn't do her homework, stays out late. What am I supposed to do with her?

This expression can be used in casual or formal situations.

figure (something) out

When you're trying to understand something, and you finally understand it, you've "figured it out". 

Aya figured out how to hook up the webcam, so now we can video chat with you guys!

You can also "figure out" a problem, which means that you find a solution to the problem:

I'm two months late on my rent, and I still can't find a job. I need to figure something out or I'm going to be out on the street.

The object of "figure out" can come in two different places: 

• figure (something) out
• figure out (something)

Pronouns like "it", "them", etc. go between "figure" and "out". Most other words can go in both locations.