I've been learning French on and off (online) for a few years. I really like it, but I don't think I've ever had this much trouble learning new things. I'm learning plural words, which are relatively easy, but the thing that gets me is how to tell whether a word is plural in verbal communication.

A few cases that often get me:

"Mangent" sounds exactly like "mange" "Fruits" sounds like "frites" When to say "les" instead of "des" and vice-versa

I know those aren't many, but you should get the point. My main question remains: How can I tell whether something is plural? Maybe the voices that I hear are bad at sounding the plural words? Thanks.