Kxl 140R suspension help

hi, so I have a KXL 140 R and I’m a rider who weighs about 150 pounds and when I sit on the bike it stinks like and it’s almost I’m too heavy or I’m unsure of how to adjust the suspension. I bought the bike from someone else and when I try and jump my ditches and I come and land, I land very hard as almost as if the suspension is wonky or something‘s wrong with it, could someone maybe give me some tips or some help as I don’t know what needs to be adjusted on this bike