how do you fire the weapons in the Soko GALEB G-2A or can u

I have no idea, where did you get it, can you post a link so we can take a look at it.
(I doubt it)

The only 'GALEB G-2A' I've ever stumbled across is this one ➡ http://library.avsim.net/esearch.php?DLID=&Name=&FileName=galeb_11.zip&Author=&CatID=root

Sorry, you can't fire any weapons. But what you can do is update the pilot's breathing

➡ http://library.avsim.net/esearch.php?DLID=&Name=galeb_11.zip&FileName=&Author=&CatID=root

I'm really tempted

its at simviation.com

http://www.simviation.com/fs2004military28.htm

I have that in my folder, an excellent aircraft as good as any pay-ware.
Look in the folder marked "docs" and click on the hyperlink you can read all about the aircraft.
Here are the key commands, no guns.
**********
Basic key commands

If you want to switch to the virtual cockpit, use key S, and Shift+S to get back again. In the 3D cockpit you can pan around, and zoom your view with keys +, -, BACKSPACE.

If you have view controls on your joystick, use it for panning view around. Default keys mapping for view panning isn't simple:

(CTRL +) SHIFT+Enter
(CTRL +) SHIFT+Backspace
(CTRL +) SHIFT+num 1...num 9

Ctrlt+E - Engine Autostart
- Throttle
- Flaps
- Rudder
- Ailerons
- Elevator
- Airbrakes
- Gears
- (Parking) Brakes
- Nav Lights, Flashing On-Off
- All Lights On-Off
- Cabin Lights
- Landing Lights
- Open/close canopy
- Eject

F1-F4
F5-F8
num 0, Enter
num 4, 6
num 2, 8
/
G
(Ctrl +) .
O
L
Shift+L
Ctrl+L
Shift+E
Shift+E (in air)

ok then what are the gun switches for

Do you see anything in the read-me about how to shoot the guns, nope. What are the gun switches for, they wanted to make it as close to the real aircraft as possible so instead of having a hole in the panel or stick they put the switches in.
This is a flight simulator not a combat game, if you want to have some good looking aircraft that shoot and fly get IL2 Stumovick, try the demo of the original.
https://forum.flyawaysimulation.com/forum/topic/11433/cfs3-no-sound-xp-sp2/