Hello Kope,
If you just need to do Pat for 128 addresses the Nat configuration should be like this:
global (outside) 1 interface
nat (inside) 1 192.168.1.0 255.255.255.128
The Nat 0 is going to be taken in consideration first and it is going to mach all the inside users so no one is going to have internet access, that is why you just need the nat for the half of the /24 range and the global.
Hope you have a great day,
Julio
Julio Carvajal
Senior Network Security and Core Specialist
CCIE #42930, 2xCCNP, JNCIP-SEC