Sure I can help you. I have a Pixel 7 on android 16 beta so very possible you have a very different problem when attempting to mod games for in-app purchasing hacks.
I had already installed this game on my phone before attempting to mod it myself. Both lucky patcher and most mods here use test signature for their mods which makes it a smooth process for updating.
I simply chose the default option for in-app purchases with lucky patcher which is Support patch for InApp emulation (Reassembly Dex). Once Lucky Patcher finished modifying the APK, I installed it over this mod and rebooted the game. Anything that costs real money is now yours for the taking
. Which isn't a bad thing considering late game I've seen some weapons costing over 9000 crystals (the highest amount you can buy in the game is 3000 crystals at a time for £99.99. You work out the maths. It's daylight robbery).
I've attached a screenshot inside Lucky Patcher showing you which option to choose.
Good luck!