I see the expression "flat-top" is not general. If so, is the expression "flat-top" in here used to describe the relationship with her father who served in Marine corps? Like hairstyle, or aircraft carrier.. and so on?

What does "peel back" mean and when's it used?

To "peel back layers of something" means to reveal or uncover something, usually something that is hidden deeply or hard to find. This expression is a reference to onions, which have many layers! Ex: Getting to know her is like peeling back the layers of an onion. Ex: Once you peel back different layers of complexity, you can reveal the core.

What does "poise" mean? Can it be replaced by "manner"?

Yes! You could replace "poise" with "manner" here. "Poise" means an elegant or controlled manner. Ex: Her poise when ballroom dancing was perfect. Ex: Tiana's manner of speaking was very poised.

What's "give me a break" mean?

"Give me a break" is another way of saying "go easy on me" or asking someone not to criticize them too harshly for something, to put less pressure on them. It can also be used when one is exasperated or in disbelief. Ex: Oh, give me a break. You'll never be as good as I am. Ex: I haven't played the flute in a while. Give me a break! Ex: Give him a break. He's still learning how to do the job.

Can you explain about the phrase “what are you up to”?

"What are you up to" is a very common English phrase that means "What are you doing" or "What's new in your life." It is a way of asking what the person is doing currently and is also a way to learn what new things are happening in an individual's life. Here are some example conversation sentences: A: Hey! What are you up to? B: I'm just watching t.v. A: I haven't seen you in so long! What are you up to? B: It has been a long time! I'm actually working at a law firm now. A: Wow, that's great! Don't be afraid to use this expression! It is very common and understandable for native English speakers. Thanks for the great question!

What does "saving" mean here?

"Savings" as a noun here refers to a collection of money that someone has set aside to save for the future. Someone's "life savings" is the total amount of money that they've been saving during their entire lifetime. Ex: The boy puts his savings in a piggy bank. Ex: I deposit most of the money I earn in my savings account.