Sorry if the following is completely negative but one can only learn from criticism.
Ok, the first and foremost thing I saw with your Marth is your complete and total overuse (wow that sounds weird to say in a Marth critique) but yes overuse of the F-smash. I understand you're new to Marth and most beginners go through the whole "F-smashing until it hits" stage but that will not work on upper level players. When you use it repetitively it becomes predictable and predictability will be your downfall.
On to the second thing. I noticed that you seem to not use the Fair that often. Know now that the Fair is a staple in Marth use. It sets up combos and is very quick which allows it to be used stealthily. Learn to use it correctly and I promise you that your Marth will improve.
Third thing. Your Marth seems very grounded. You should learn to approach with SHFFL'd aerials rather then just walking up and f-smashing or grabbing (not to say those aren't good approach methods when used sparingly but not how much you used them.
The following things are more situation focused:
In your vid against the Falco at 1:37 you threw the Falco up and then waited on the ground for him so you could land a, you guessed it, F-smash. Luckily, you were able to hit the Falco with that very predictable attack but such won't be the case on upper level smashers. When your opponent is open in the air like that you should take that moment of vulnerability and sieze it. You should have followed that throw up with a Fair or Nair.
In the vid against the Marth I noticed a few problems.
Once again, at the beginning of the match when the opposing Marth was in the air you just remained grounded. You should have gone for the aerial offensive.
Sorry about repeating myself but, at :43 you had the opportunity to throw out a SH aerial on your opponent. I think if you would have hit with the right part of the sword you could have even landed a Ken Combo and any time spent not Kening when you could be is time poorly spent. LOL.
The last thing, at 1:28 you grabbed your opponent and then just stood there. Why? Atleast hit him with the little kneeing thing never just stand there.
Well, I hope this was helpful.