This isn't a guide, more of an explanation if you're struggling as I am currently. I actually have this achievement even though I only have 19 challenges done, no clue why. But as of right now, if you join someone's coop game its possible to glitch most if not all of your challenge progress (including the wingsuit ones need for that achievement as well) as of right now, there's no known fix for this so unfortunately we have to wait for a patch. Just wanted to let anyone confused by this know why it's happening.