Yes, you can use it to mean "almost", "almost", "most of", "kind of", "sort of", "basically", "for the most part", etc. It is very versatile and casual.
I pretty much don't understand what you're talking about.
I read pretty much all of the book.
That was pretty much the hardest test I've ever taken.
If you don't know the right word, you can pretty much just fake it.
I hope those examples are useful and not confusing.