Match 1: Hey buddy. Sure I'll give you some tips. Ok at 00:22 you grab the ledge for the edge guard. But when you grabbed the edge you just hung there. You should always renew your invulnerable frames by grabbing the edge, letting go, repeat. If you kept renewing your invulnerable frames then you could have went in for the bair or ledge hop dair kill. The funny part is...the blue Marth started to do what I was just telling you after he recovered. lol
Anyway, work on your DI. That back throw to forward smash shouldn't have worked. I also wouldn't recommend using ledge hop uair, especially on another Marth. It lacks frontal range, which is what you need in ledge hop attacks. I'd stick with ledge hop nairs. Oh and ledge hop wavelands are also an extremely useful tool to use. Just make sure you have invulnerable frames during the first part of the waveland. Again, at around 1:06 you got hit during your edge guard cause you didn't refresh your invulnerable frames on the edge.
Work on l canceling those dairs. I think you missed them quite a bit. When you get grabbed by Marth, start to DI away. Forward throw to forward smash shouldn't work on ya. Also, notice how the blue Marth killed you with bair with his invulnerable frames. Oh and using Marth's tipper down tilt is also an awesome edge guarding tool.
Match 2: When you get up thrown by Fox don't be so quick to double jump. Just start DI-ing away as soon as Fox grabs you. Oh and coming down with a dair while falling back to the stage isn't a very good idea. At around 00:20 Fox is on the edge yet you are standing in the middle of the stage. You are Marth, the best edge guarder in this game. You should have been over there as well applying pressure with your down tilt.
The ideal spot you want to be edge guarding with Marth (against anyone) is close enough that the tip of Marth's blade during his down tilt barely passes the edge. The reason is because Marth can cover all possible recovering attempts from the opponent. So if the down tilt misses and your opponent grabs the edge, just stand up and wait/watch. If your opponent jumps from the stage, jump up and uair/fair them. If they roll onto the stage, turn around and grab, back throw. If they simply get up...wait for a possible spot dodge and forward smash them. But keep in mind, this only works if you are in the "ideal spot" I mentioned earlier.
Good job in removing the Fox's third stock. Never double jump like you did at 1:42. Simply fall towards the edge and grab it, OR towards the stage and air dodge. The counter was a ok idea, just not the double jump. An awesome approach you should use is dash canceled down tilts. If your down tilt hits at lower percents (must be a tipper down tilt by the way) you can dash in an grab.
Overall...you aren't bad at all. Keep it up. I enjoyed your matches. XD