I only really analyzed the second match of the first GFs set. The first match just seemed like you had a very strong start, but almost choked the game away with a series of rushed, hastily made decisions.
Lolz, how many bans did you have and why did you leave this stage open? Out of all the small stages, I guess WW is the best after FoD, but it's still too small and Marth can easily reach the plats with fsmash and other moves.
3:07:15 - Not a bad string you had going right here. However, your major mistake was in trying to follow him the way you did. Your main concern should have been to try to get to ground-level before Marth so you could maintain your positional advantage. Instead, you jumped out and let him get under you, which is the worst possible place for him to be. If anything, you could have maybe tried to follow up with a laser or gyro snipe, but jumping off like that wasn't a good idea since he can immediately rebuff anything you try with his own more disjointed moves.
3:07:15 to 3:07:24 - This is all the result of that one bad choice.
3:07:33 - Not exactly sure why you ran all the way across the stage to let Marth back on for free. Maybe you weren't confident in your own superior position? One of Marth's weaknesses is getting off the ledge, especially against chars with good CC games. If you stay just out of reach of ledgehop aerials, you are in a good position to heavily pressure any attempt he makes to get back on. If you go a little closer, you can bait out certain unsafe ledge options, such as ledgehop fair, and punish them with a CCC. You were at 0, so that was easily feasible, and with the ledge invincibility limit, just maintaining that position forces him to make a decision or you can start hitting him. Definitely shouldn't have just dashed away like that...
3:07:36 - Personally, I would have tried to snipe him with a laser here after that dsmash to tack on some more damage and make his recovery back a little more difficult.
3:07:38 - Again, why are you trying to jump out at him like that when he can stuff you with any move?
3:07:54 - Alright, spamster... Random boost nair into two dsmashes? The first move was a hail-mary attempt, the dsmash was a panic reaction to missing at point-blank range, but the second dsmash was just scrubby.
3:08:18 - Can't really blame you for the trade not going your way like that. However, with only two boosts left and Marth standing right by the ledge, I would have either [fast option] immediately boosted forwards for the low platform (and prayed that Marth didn't read that with a tipper fsmash) or [safe option] boosted upwards and hoped that I could juke Marth out with my options of aerials and landing on/dropping through either or both of the plats. With that safer option, even if Marth read/reacted properly and hit you, an aerial probably would not kill and you can DI that high to make your chances of getting back even better. All you need to do is get your feet on the ground for an instant in order to get your full recovery back. That should have been the prime objective here, not trying to make a low recovery for the ledge.
3:08:31 - I know we're all fond of the gyro, but seriously, you should have left it. After that dsmash, you could have immediately tech-chased him for free on that platform with an assortment of moves (I would have gone for dash usmash, but you also had utilt and all of your aerials, boosted or not, at your disposal). Going back for that gyro cost you your advantage, and you didn't even get any positional advantage off it. You immediately threw it away, and didn't go nearly as far as you would have gone if you'd just dashed after Marth immediately.
3:08:36 - You are trying to spot dodge > (CC) dsmash way too much. You've kinda been doing it all match whenever Marth was really close, but it was excusable until now. Your wake-up call should have been when you tried to nair into two whiffed downsmashes earlier and Marth just baited them out and daired you. At this point, the Marth is just spacing himself so you can't hit him with CC dsmash. Now I'm not saying that CC is a bad idea, but the
dsmash is what's really bad. You could, say, CC shield and aim to WD OoS after Marth's next move. Not only was your choice of dsmash punished, but you're spamming it so hard in this really bad position that you ended up doing dair offstage.
3:08:40 - The gyro was a really good move, but you should know that moving forwards is enough of an action towards taking the ledge that it will bait Marth into upBing early, especially since the gyro missed. I would have used this to bait the early upB and punish it with dtilt or dangled fsmash.
3:09:00 - Rule of thumb is that you want to stay under Marth because that is where he is weakest. You could have easily reacted to this get-up roll with dash usmash, but you went for the non-guaranteed nair, which was directly punished.
3:09:10 - Not gonna condemn the laser choice, but gyro may have been more suitable here. Would have limited Marth's options and then, once safely behind it, you could consider shooting a laser or something.
3:09:15 - So I was actually expecting you to get fsmashed here, because that was not good DI. At this high of a %, I believe Marth can only get a kill combo off of fthrow, so once he grabbed you, you should have just been holding the stick down and away. In any case, doesn't really matter because he didn't follow up. However, afterwards...
3:09:17 - ...you should have done anything but that. It's endgame and you're at very high %'s. Your only goal at this moment should have been to get back onstage whilst avoiding ALL of Marth's kill moves so that you could get another shot at taking out Marth. With this in mind, the best options were to either boost for that close high platform or keep boosting past it and try to land somewhere past Marth. Going down and trying to hit him with one of your slowest moves was a very bad idea, and it was a no-brainer for Marth to just keep his extremely advantageous position and utilt you.
All in all, your play wasn't that bad. You had pretty good punish strings and you were willing to push him very offstage with your combos. However, your decision-making needs some work. There were a lot of times when you overextended yourself and gave up your advantageous positions, others when you gave up free follow-ups for arbitrary things like picking up the gyro, and others when you tried to challenge Marth in positions where you really should have just been looking for ways to recover around him. You also have a bad spam/panic reaction habit, and going by this game, it looks like he'd completely adapted to it when he had the advantage, so one can understand why he 3-0'd you in the second set. You did have some nice glide tosses, though.