can someone recommend a tutorial on how do i determine whats wrong with an audio and how to improve?

I have an online conversation video. i hear one of the participant is like speaking from a bucket. My biggest problem is that i dont know how to analise audio file what to look for and how to improve its quality. I want to learn it from somewhere. i can imagine something like it supposed to be x value if it is female voice and use this and this effect and watch this and this value. Now i am just doing random stuff see if it makes it better instead of approaching from a professional level as i dont know it yet. so any recommendation for audio workflow tutorial for online call videos?