Kral Arms Puncher Big Max .22 Leaking Air over night.

I can tell you're new because of how beginner is spelt. Jk

Getting some leak detector would be a good start, CRC makes a great one. Or you can put a bit of dishsoap in water in a spray bottle and gently apply some. Once youre done blow all the soap and water mix off. Leak detector is better as it leaves no residue and its cheap. Auto parts places should have some. You can tape a bag over the end of the barrel also and see if it inflates. That should get you started