KCCO, the way the shots on your target are placed it's highly suggestive of some bad flinching. I'm basing this on the fact that there's no real roundness to the group. Instead it's more of a pie shape extending down and to the left. Is this your first center fire handgun?
First off don't even try to think you can hold the gun back during recoil. Just mellow out and be as "dead" a lump as you can. You want a good grip on the gun but not a death grip. Too tight is just as bad as too loose. You want to hold it like you would a good firm handshake with a friend. Or if you play sports like you do a baseball bat or tennis racquet.
Next up don't just pull to the BANG! and then let go. Commit to a full pull all the way to the rear travel limit and HOLD it there through all the recoil. That removes your focus on the upcoming noise and kick and puts it into a proper trigger pull and proper follow through.
When you pull the trigger realize and remember that it's not a video game switch trigger. Build your finger pressure up in a steady and smooth manner over a roughly 1/2 second time period to start with. A smooth build that sees the trigger break at a point which surprises you. But as I said above don't stop. Your job is to pull through the break and hold it back all through the recoil kick.
Practice this 1/2 second to full back pressure build with some dry firing as suggested above. And while you're doing that be sure to feel for the rest of your grip altering. The ONLY thing you should be moving is your heart, your breathing and your trigger finger when shooting once the sight picture is set.
If you have access to a .22 handgun I found for me that the .22 is a great "trainer" to transition from dry firing to actually shooting. The lower noise and kick of the .22 allows me to achieve the needed flow and then I can transfer that to the center fire gun. When I felt the flinch return I'd go back to the rimfire until I had my focus again then try some more center fire. It took quite a bit of this along with focus on the factors I described above to beat my own flinch.
