corneria
too much nair when it's not safe, even being used as an approach. use explosives to force opponents into it, retreat with it, use it rarely if you're going to just throw it out when you don't have the upper hand and it could put you at risk
after you took his second stock you just kind of stood there, he promptly sent you into the air and juggle trapped you to death. when you get the kill get the hell away and start setting traps up. you also could have gotten out of that but you were preoccupied trying to attack when you were not in a good position to do so, the C4 wouldn't have hit anyway in that circumstance
grenade use seems to have been sporadic, two times during the match you used them a lot and then like, forgot they existed...also don't think I saw mortars much, snake is all about cover fire, most of your moves are punishable if there aren't explosions going on all around you. you spent a lot of the match just straight up fighting him when marth has the speed and range advantage on you if you play that way, using snakes various bombs for stage control and narrowing opponents options are key
too lazy to critique the other match in depth and a lot of it seems to be similar, although you did better up until like 2:20, at that point you were probably just looking for the killing blow and he caught you in that mode and took advantage of it
hope that didn't come off as all negative, just focusing on that since you asked for advice
also lmao at "my utilt is broken!"
EDIT: angel is right, dthrow is too awesome. when you use it, keep in mind that just by standing next to them and shielding, 3 of their 4 options will get them ftilted or regrabbed