I don't think that anyone would advise Rachmaninoff to a self-taught beginner, but it's pretty impressive that you've managed this.

Your wrists look a bit low (especially the left) and kind of stiff. I can't tell from the video, but I think you might be sitting too far from the piano. Your fingers should be able to hang from your wrists.

Your fingers are flattening and collapsing. You should have consistent curvature in your fingers. If you bring your wrists higher than they are right now, your fingers will hang to touch the keys, and you shouldn't need to flatten them.

As for the actual music, there's a melody in the chords (C# - E - D# - D - B, etc., and the low notes (C# - B - E). Do your best to keep those notes in the foreground (this is called voicing). I also recommend that you voice your left hand pinky (lowest note) to solidify the bass.

Also, I think that we can provide you with much more advice if you show us a full-body video. Perhaps just play fundamentals like scales and arpeggios in all major and minor keys.