I'm going to ask more of the ''why is that so' questions today.

I have to write down a dialogue from a movie I watched today to lay the foundation for my first two questions.

A critically ill girl sits on a bench in the graveyard. The girl's friend comes up to her and the girl says:
- G: Big ups for finding me
- F: It's a rather morbid choice of resting place
- G: I came here a lot when I was a kid. Sometimes you just need a place to think, you know.
Some unimportant stuff
- F: I'll take you somewhere else, somewhere safe.
- G: Okay, but can we stay here a bit longer? It's nice. Unless, you have somewhere to be
- F: No, I'm good

1) Why the friend says '... of resting place'. Shouldn't it have been '... of a resting place'? I've been noticing that sometimes countable nouns go with no article at all. Is it because they're used in set phrases? Or maybe there is a rule for when you should not place any article before a noun, even though the noun is countable? Please, help me work through this thing. It would be impossible for me to get to the desired level of English thinking untill this stuff is dealt with Right now it plunges me into total confusion. One more thing, the last thing of this kind I can remember right now is "heat of battle" rather than "heat of a battle"

2) The last phrase of the dialogue, which is "No, I'm good", just stuns me. Yeah, I know that it basically means that the friend doesn't have somewhere else to be, but the logic of the phrase is just beyond my comprehension. Please, someone tell me why this phrase was ever even used.

3) I've seen a lot of sentences of this pattern on the internet.

-- how do/would I do that.

I ask that because we don't really ask themselves 'how do I do that' questions. In fact, it would be transformed into an infinitive form as this - how to do that? So, the question itself is this. Do you ask themselves "how do I" questions rather than "how to do" ones. I think it'd be invaluable to know that if I want to achieve what I seek.

Well, I still have some questions but I think it's a rather long post already. Don't want to take too much of your time. I can't wait to see your replies and thank you in advance