What would you take first ?? Please help me with advice

The advise would be a little different because you are from Croatia.

Yes, do the brass and bronze.

The electronics boards might not work for you because it wouldn't be profitable to pay to ship them to a buyer here in the United States.

I wouldn't recommend breaking down the boards with a heat gun for different reasons.

1: There are poisons that are released into the air when you heat a board. These can make you very sick.

2: There's the problem of how to dispose of the depopulated boards responsibly. ( Just throwing them in the trash isn't the right thing. )

3: You have to patiently pick through all of the different bits & pieces after they have been popped off the board and sort them out. ( It takes hours. )

4: That's waaaay too much like work !