00:11- You had the advantage in posistioning here? Why did you roll? The instant you did that Ganon had control of the fight. And you got hit becuase of it.
00:13 - You ate Ganon's boot twice. You should have backed off after that first hit and re-grouped.
00:16 - No airdodge.
00:36 - BLARGH!!!!! lol. Eh. Probably should have went for an edgehug here or just let him back on. Since Marth leans in for his F-smash Ganon was able to grab your arm and take you down with him.
00:53 to 01:00 - I'm seeing alot of smash spam. Reign that in. Marth's smashes are for killing. Not punishing.
01:26 - There is no reason why you should have rolled into this. Roll with purpose and not out of habit and stuff like this will never happen.
01:31 - Where was the tech? You also DIed TOWARDS Ganon. For what? You made it easier for him to wail on you.
01:35 - You should have survived that. Nuetral b to move back towards the stage then angle your up b instead of straight up.
02:00 - Missed an easy chance to punish.
02:09 - You ran back when you had an easy edgeguard. Don't willingly give up advantageous situations like that.
02:15 - Should have edgehugged. Ganon would have been gone. Or used Dolphin Slash to grab the ledge.
Ok, you seem you have the basics down which makes things easier. But you have some bad habits that are common of all Marth players at one pont or another. First off, you don't punish mistakes that well. Your friend is playing Ganon, a character that Marth runs over because of how easy it is to punish and edgeguard him. There are two things that you didn't do well enough.
Your friend left himself open soooooooooo much. He spammed f-smashes and Warlock Punches, which is easy for Marth to punish. You also didn't punish with Marth's all purpose punisher, the Dancing Blade. Most of the time you opted to punish with F-smash. Don't do that. Dancing Blade is THE move to punish with. It's fast, does good damage, regenerates itself as well as his other moves. It's Marth's best move IMO.
Another bad habit you have is giving up your advantage. There were times where you would get a hit then not keep the pressure on, or you rolled away or dashed away. Don't do that. In a game where combos are virtually nonexistent, momentum is everything. Once you get in a hit push your advantage and keep the pressure on. You MUST keep control of the fight for as long as possible, but you musn't be reckless either. Let's say you get a hit with a SH fair. Well anyone good knows that you can't chain Fairs successfully, so if you try they might hit you back. So you DI just enough that you keep your spacing, and you fast fall back to the ground. This way you can continue your advance and pressure your opponent safely.
You need to also work on implementing Marth's other moves. I saw plenty of smashes and fairs. I didn't see a single tilt. ALL of Marth's moves are good so use them. Experiment with all his moves so you become more well rounded and have more tools to work with.
Also I have written alot of stuff in the Marth boards, so you might wanna check that stuff out if you wanna learn more.
Well, that's it pretty much. Maybe someone else has stuff to add on. Hope I helped.