Your Falco's too slow. More laser pressure, JC your shines more quickly, and follow up your aerials more quickly. You've got the basics down, but your Falco's still pretty rough. First, don't rely on spotdodging and shieldgrabbing so much; it'll only get you punished, so use both techniques sparingly. Don't try to CC and dtilt for kills, since it's really obvious, and relatively easy for your opponent to space it so you'll never get the dtilt in. Against Sheik, it's better to just fthrow at higher percents, make her upB onto the stage, then just bair/dsmash/fsmash during her afterlag.
Use Falco's laser game to shffl more, since you fulljump/doublejump way too much. I find that Falco's very vulnerable while he's in the air like that. It's better the approach with shffls, and if you do double jump, fastfall it so you minimize the amount of time that you're vulnerable in the air. Also, work on better using SHL, since in the first match on YS against Sheik, lasers didn't play a large factor at all, and you should be using them to control the flow of the match.
It seems that when someone even slightly pressures your shield, you ahve a tendency to roll. If you're going to roll, at least roll away from them, not behind, as it makes it slightly harder to chase. Another option that's viable against Sheik is shine out of shield, which can be a nice combo starter for you as well. It's also wise to crouchcancel a lot of Sheik's moves when you're at lower percentages, such as tilts, since you can just cc into a shine and start comboing from there. However, CCing at higher percentages will lead to your dying as Falco, because it's quite predictable at higher percentages what you're trying to do.
Learn LHDL. It's a very useful tool to add to your ledge game.
When you double jump too much, you're not pressuring your opponent at all. Falco's pretty much all about his volatile rushdown game, as you can go from just SHLing/RSHLing right into a combo, and your opponent takes upwards of 50% in a few seconds. So you have to be able to take advantage of every little opening that your SHL game presents to you. That's why it's usually preferred to shffl aerials, that way the pressure is constant, and leaves no breathing room for your oponent. Go watch some Falco vids, and you'll see that every Falco utilizes lasers very well; proper laser gameplay can often decide the outcome of a match.
Good luck, hope this advice helps.
