Newish here too, had my DE MWS a few months now. So take what i say with a little salt, but from my experience and research -
Firstly, the Bolt needs to be forward, and the gun has to be primed. Just rack the gun, and punch out the pins.
Secondly, especially with green gas, you need to swap the nozzle return spring. Bavtac make the best out there afaik.
Thirdly, Its a whole lot of maths and physics, but Gas guns are prone to this thing called Joule creep - far more than their AEG or spring counterparts. Without going to jargon, you'll notice that heavier BBs have proportionally more power than they would with AEGs. To remedy this you'll want to get this thing called an NPAS. The best one out there is the Federal Concepts NPAS/ FEDA valve (However they're out of stock right now, as he's swapping to a newer version, shouldn't be too long until they're back in stock), followed by the RA-Tech, then the Angry gun.
Sub-Note, using weaker gas is actually what the TM system is made for, green gas is stronger than what the system is designed for, so using duster gas (otherwise known as 144a) is also a perfectly alright alternative to installing an NPAS.
Lastly, after every game day. Especially if its outside, and especially with green gas. Explosive enterprises made a good video on how to maintain your gun, but its mainly - wipe the barrel, wipe the BCG, wipe the visible parts of the lower and all of the inside of the upper, apply lube where needed, and go.