There are hard missions, and easy missions, but I do my best, when people just can't do a hard mission, for now, only these are available.


Tutorial:

Windows XP, Vista, 7, 8, 10
Click Start Menu Button (on keyboard) + R
Type "Documents" and click enter (or "My Documents" on windows xp, on windows 7 it gives access denied for me)
Open "GTA San Andreas User Files"
Change the "GTASAsf1.b" number (1) to any number from 1 to 8 if you have free save place, or you can override.

I don't know about mac users.