New investor, Need help understanding the lending process

[Edy Lagares]

So my goal is to find a multi family (2-4 units) property and house hack.

I applied for my first loan ever and got pre-approved for $250,000 but I don't know what to do next.

I guess, I want to know if after all this effort, giving all these documents and information, is it ok to say no if I think it's not a good deal?

Being that this is my first loan and my credit score is not great, What should be a good deal? What should I watch for? 

Can I try to get another loan on top of this one if I want to get something that is more expensive?

He said I can't borrow for my Down payment, is that true?

What questions should I ask the lender?

I appreciate any help I can get on this. 

This is exciting and scary at the same time, I guess that's how's supposed to be?