^^^ Taz made some very valid points there. Tony L and others have given some good advice too.
I would add one or two myself.
Shoot the Walther a lot!
Find the best pellet for the barrel. Put a tin or three of pellets through it. By then it will be running in (if not perfectly run in it should be well on the way). The recoil and grouping will improve as the gun runs in. You will adapt to the feel and develop the hold and your accuracy with the gun will improve as your gun smooths out its firing cycle. Check you are getting consistent MV's, if you are then don't tune it/detune it or mess about with it other than adjusting sights, trigger and hold if you need to.
When you have shot a few hundred pellets (at least 500) it may be worth re-testing your grouping with some of the pellets you may have rejected initially as a gun can run in to like a pellet it initially did not.
When you've got the gun fully run in and have adapted your hold, stance and technique to get the best you can from it then compare it to another gun but in my opinion it will take a good session to decide if another gun is actually better/worse than yours, a simple 10 pellet group won't tell you much!
I have watched people change gun after gun in the search for "perfection", trying however many tuning kits and scopes and springs and lubes with each new gun and never actually getting truly happy with any of them, often going back to "I wish I still had my old ... I had years ago, it was excellent, wish I'd never sold it, I'd buy another today..." etc.
Take time to learn the gun, no matter how good a shooter you think you are it takes time to get settled into a new gun. I have a couple of very old HW80's that I cling on to, I have had many other springers over the decades and keep going back to them. Not many people would call them a competitive target gun but I'd be happy to take one out for a HFT competition tomorrow, at least I wouldn't have to gain a new "muscle memory" for a new gun (but then again I'm well rusty!)