how can i fix or replace oil pressure sensor?

Maybe, if you let us know what engine type you have.
As a rough guess, I'd think buying a new sensor would be better than trying to repair a failed unit. Normally a simple job, locate sensor on engine block, disconnect wire, clean area around sensor, unscrew old sensor and fit new sensor with new sealing washer. Tighten to correct torque setting, refit wire and job done

Rupert
December 2019