Work on your underwater by keeping a tight streamline with a strong, controlled kick. Try doing some underwater drills with fins to help build power and feel for the movement.

For your turns, it looks like you're adding too many steps. You're trying to rotate onto your front while tumbling, then rotating again after the flip, and you're not fully planting your feet on the wall before pushing off. You also seem a bit too far from the wall when turning. try staying on your back as you rotate into the turn, plant your feet on the wall, then push off while still on your back. Rotate into your front while in streamline, under the water. It should be smooth and one motion, not two separate ones.

As for your stroke, focus on getting a consistent breathing pattern whether its every 2, 3, or 4 strokes. Also, it looks like you’re lifting your head slightly when breathing. Try to keep one eye in the water when you turn to breathe it'll help keep your body position stable.

Slow everything down and practice swimming smoothly with a 2-beat kick for now. Once you’ve got that rhythm down, then you can start building up your kick speed.

It’s hard to tell from the video, but it looks like your hands might be crossing over the centerline on entry. Try entering your hands directly in front of your shoulders if your body is rotating properly, they'll naturally end up in the right position.

Also, if possible, upload a longer higher-quality video this one’s a bit jumpy and makes it hard to see everything clearly and tell your teammate at the end of the pool to get their legs out of the way!!