Remove the forend - one screw, and a large screwdriver. Clean the gas system. If it has never been cleaned it will be encrusted.
The pins that secure the trigger group are not difficult to push or tap out. They are retained by a spring detent system. Then just wiggle the trigger mechanism out. You will be able to clean the mechanism. A spray cleaner can be used; keep it off the wood.
Further disassembly is a pain. To get the bolt out, the barrel must be removed, and there is a nasty little pin that retains the cocking handle. Not necessary, unless there are defective parts.
Make sure the chamber is clean. If it isn't, extraction is more difficult, and this can cause functioning problems.