If it's sticking or very tight with the crank handle you need to disassemble, clean and inspect everything. Once you get the sunroof panel out you'll see how it works. Basically the crank gear moves the cables in opposite directions thru the guide and cable troughs by cranking the handle. Very simple setup.
It's easier to do than to explain so just do it. Kinda like minor exploratory surgery.!:-D
There are very few parts actually in a manual sunroof assembly.