Christian,
You took time to shoot, load and post and I disagree with a few of the responses - so I’d like to add my two cents. Let me kick that off with something positive…nice recovery, I like how your elbow is high and your wrist/hand is low and you’ve got a good lookin’ triangle there - it’s nice. As is your long axis rotation which - yes, is a bit more to one side than the other but c’mon that’s not a priority at this time.
Now, on to the fixes.
The number one priority in swimming is reducing drag. You can forget about trying to creating propulsion until you reduced the major drag. I’m shocked that a forum such as this where “aero” is sacrosanct that we’d overlook that. Seeing as how water is 800 times thicker than air you’d think we’d care more.
You have the number biggest drag: body drag - your hips are ~5 inches below the surface of the water and your feet are ~10 inches below the surface so you’ve got drag at chest, stomach, hips, thighs, knees, shins and feet. You could attempt to “get level” with a harder kick but I don’t recommend it. You should find balance and get level in a more efficient manner - if you choose to kick harder down the road let that kick be about making you go faster not about leveling off your body.
The body in water is kinda like a sea-saw on a playground : when something in the front goes down something in the back comes up. We have three tools with which to solve this: lead arm depth, head position and pressure. You’re a bigger guy with lots of muscle and not too much body fat (probably dense bones too) so your legs want to sink and you’re gonna need all three (arm depth, head position and pressure) to get level. You’ll end up riding deep in the water but depth doesn’t matter just being level matters - on a side note, I’m built like you, many of us are this is not a detriment to swimming fast.
You already have a deep entry on the right arm so leave that for now but put the left arm on a trajectory of entry so that it too goes as deep as the right (down the road it can shallow up some so you send energy forward more - but for now get 'em both deep). Your head position is pretty good but many still need to tilt down just a hair - you have a good head position on your push off but it creeps up a bit after a few breaths and, again, with your body type you’re gonna need every thing you can get. Lastly, and this is the biggie for you, you need to press down on your upper chest. While you swim think about keeping pressure on your arm pit and then as you roll move that pressure across your collar bones and on to the other arm pit. That pressure, combined with existing entry depth (I’m talking about your arm going in deep as it does now) and a slightly deeper head position should get your hips very near the surface and your ankle bones just an inch or so below.
The left arm cross over is a bit of drag too - for that I just say this: in the water when we move something a millimeter it feels like a mile so you’re going to need to swim with the mantra of “enter wide, extend wide” and it needs to feel crazy wide to probably be right. There’s a down side to this… by focusing on “going wide” to fix the cross over it will work against the fact that you pull too wide and need to be pulling under the body BUT I urge you to put that off for now and just focus on getting the body level and solving the cross over - reduce the drag, you’ll be faster with less effort - then you can fix the catch the arm sweep, the finish and add in kick if you must.
One last thing - trying to improve technique in swimming is not about the old saw “practice makes perfect”. It’s about “perfect practice making perfect”. What I mean is this…swim short bits: 25s, 50s, 75s. Swim them easy. Rest a ton between each piece. Forget about trying to get “fitter” by swimming faster or longer sets or less rest - just swim for technical perfection now and improve your fitness via bike and run.
You’re needing 25 strokes to cross that pool (not sure it it’s yds or meters) but at your height I KNOW you can swim that speed at ~20 strokes by just fixing your body position so go after that first and you’ll feel a break-through quickly if you swim often with focus and purpose.
All the best, Ian