How a can get the sort cut to de mumburi complex (the caves)
Which short cut do you refer to? Do you mean a short cut underground way between old crypt and munbury complex right?
If that so, you can unlock a shortcut way by exploring a munbury complex at middle-bottom (the same row with a gateway to Zombie town) there will be a hidden gate appear (not sure that it require certain perception point to find it or not) and it also RNG so you can walk left and right until you find it.