Hi Nikita,

re:
> How can I close that hole and how I can boolean the cylinders from the main object?

I've attached a version here that has the hole patched up. There is a little edge in there that is making things a bit difficult. I ended up untrimming the surface above the hole and retrimming it with a line that matched up to the little edge better, then i was able to join together the little edge with its longer neighbor and use Construct > Network to make a filling piece.

- Michael