My chef sim used to get promotion usually in 2 days but now it doesn't fill even half with work hard mode, I just want to get back to normal speed. How can I get it back?

The options you seek are on NRaas > SP > General Options > Options:Careers > Options:Job Performance. You might want to switch off Adjust Performance to Age Span. If you are playing relatively long age spans, SP will by default compensate for that by making it take longer to progress within a career.

Ahh thanks!! Yes my sim's young adult lifespan is around 300 days until adult.

Another setting to also check on is Nraas>SP>General Options>Options:Careers>Options:Job Performance. Alter Performance Decrease Rate that one does the same thing except it changes decrease rate so on longer life spans you might want to set that one to True