Hi, native speaker friends:

According to the grammar I learned, verbs should be modified by adverbs, right? But I've noticed native speakers prefer to use adjectives, and it seems to be so mainstream.

For instance:
Hire me. I work cheap.

Eat healthy.

He's real good.

She works real hard.

I can't think of other examples for the time being.

Can you tell me if the above-listed sentences are acceptable?? Thanks!