Well, you are off to a good start, but you have a lot of room for improvement. Dittos can be pretty hard to gauge skill in, but as others have said, both of you play pretty straight forward.
Learning to bait moves is an important skill. You are playing against Marth, so you should know his attack range (since you are playing him as well), use that to your advantage by getting extremely close to his attack range. Both of you guys use F-smash a fair amount. That's not necessarily a bad thing, but it can be punished a lot easier than most of Marth's aerial game.
You don't seem to be able to chain combos that give you momentum. Momentum is very important in a match, and can psychologically win the battle for you against weaker opponents. All of your combos seemed to be at most 3 hits, which doesn't build a lot of momentum. I don't have any example combos for you, but you might want to look into the Character Specific Forums, or watch some videos of some better Marth players.
You also don't edge guard/hog enough and/or properly. You spam f-smash when the opponent is off the edge like that's supposed to keep them off, and your Marth friend was pretty much able to grab onto the ledge every time because you released too soon, or he used his up+B at the right time so the f-smash couldn't reach him. Edge hogging could've easily taken a stock off your opponent a few times in those match videos, but you hung on the ledge and got hit, instead of rolling (they cannot grab onto the ledge while you are in the rolling animation from the ledge). You don't spike when given the chance at the edge, and it's really not that difficult (just be sure you land on the stage from a SHFFLed d-air, and don't fall off). Edge guarding is important because it can allow you to get kills at very low %, giving you a one stock (or even more) lead on the opponent.
You also don't SHFFL very much. I know Marth has the SH double F-air, but I did not see you use that at all, so you should probably be SHFFLing. SHFFLing is Short Hop, Fast Fall, L-Cancelling if you're not sure what it means, and I'm almost positive you know what each of those techniques are based on the match videos. SHFFLing can be intimidating. It makes your character seem faster than he/she really is, and it also allows you to react faster to many situations.
You also use up+B WAY too much. There are times when you get hit when you're trying to edge guard, and you instantly use up+B sending you way above the stages' surface. That is a very, very unwise thing to do in many cases. It makes you vulnerable to air juggles for a considerable amount of time. What you should do (when possible) is air dodge back onto the stage. Air dodges take considerably less time and can allow you to gain control of the match for an entire stock, depending on who you're playing against. Air dodging doesn't work in all situations and sometimes up+B is the better choice, even if it puts you high into the air, but I'm not about to go into the situations where that occurs, you will find them the more you play.
Another thing to do is spam "safe" moves. When you're not in range to attack the opponent, and they can't snipe at you, spamming SHFFLed n-airs and f-airs is a good way at keeping the opponent at bay, and even a safe way to approach in many situations. This isn't some end-all tactic either, but the more match videos you watch and the more experience you get, the better you will be able to judge which situations not to use this (doing this against Falco's lasers is a bad thing, waiting for the right moments to f-air against Link's and Peach's projectiles can be a very good thing).
Just food for thought, and good luck in your smashing!