I was going to say, I don't see Marth's jab reset enough OUTSIDE of chaingrabbing. It's pretty standardized during chaingrabbing but not really done very much on the fly.
Anyways, Stelzig:
-It feels like you're in the process of piecing this matchup together. Once you get your hands on him, you seem to be able to punish solidly. But yes, getting your hands on falco in the first place is the hard part so lets take a look:
-I don't see you utilizing wavedash/waveland OOS enough. This will help you bait some poor approaches and give you some better responses to shield pressure (WD oos fsmash is cool if it's working, otherwise WD oos to DD grab/dash attack). When you're underneath a platform, shield a laser and hop oos to waveland on to the platform. Then you can come down off the plat with a fair approach if you think it will work, or you can just chill on the plat for a bit to really make him think about what to do (it's actually kind of awkward for falco to attack you when you're on plats unless he's directly under you).
-I like that you're allowing lasers to just hit you, and not panic shielding after them to further immobilize you. Now what I would recommend, is walking while being hit by lasers. This can help you set up more ideal spacing when Falco is lasering you from too far for you to do anything to him. I see you trying to ftilt him out of taking lasers. This is good, you just need to learn the spacing for which this works a little better. Another thing you should work in is immediately dashing away after taking lasers at closer range. You'll bait approaches like crazy and get pivot grabs out of it.
-Further expanding upon this point of falco being far away from you. Your powershields aren't doing much because you're so far away from him. In general, whenever I see you drop a combo or miss a tech chase and neutral position resets, it seems like you voluntarily give falco a TON of room to restart laser spam and ultimately approach on his own terms. Just because you missed a tech chase does not mean the pressure is over. You want to be in falco's face. He will break you down if you allow him to laser you endlessly from all the way across stage. I'm not saying you need to be overly rushing him, but stay "in his face." Don't let him feel comfortable lasering. If you give him as much time and space as you're giving him, it's his advantage, not yours. If you close the space he'll be more likely to give you an opening, plus, as you're already doing some, you can get dash attacks out of the closer range fighting.
-dash attacks are amazing, look for them even more.
-be wary of spacies bair. You're running into it a bit. Understandable, it's one of the best moves in this game, but being aware of when you are and aren't safe from his bair is very key for survival.