Remove background noise, Audacity strips away dialogue quality

Hello.

I have some audio I want to clean background noise (a refrigerator in a restaurant running loud on one audio file, an AC unit running on the other)

I've used Audacity to do this, yet, I find that the quality of dialogue in the audio clips diminishes to where it sounds partially digitized.

Can anyone advise on what to do, and/or recommend software that can assist me?

I'm willing to pay for software (as long as it isn't too expensive).

Thanks in advance.