Just to make sure, are you running on Low resolution (best performance) + FSR on Ultra or Quality? And have disabled sweat? I had a look at the device specs, and it's a pretty entry level phone by today's standards. I'm surprised tbh at Hell arena giving you the highest fps - but I'm guessing it's probably because it's quite low poly and only uses 3 materials - which means few draw calls. I'm speculating though, because if you bring in a lot of clothes into that arena you'd increase the number of draw calls significantly, so if that's not the case... I dunno.
For a bit of context - the game is as optimized as I could get it (there are still some optimizations that haven't made it to the free versions yet that I made a few weeks ago, concerning sweat and getting dirty - but those shouldn't be that significant), but there are some things that were intentional and deliberate design decisions, which are creating more work for the GPU:
- Models are a bit high poly, and that's intentional, due to the game focusing on physical interaction.
- Clothes will cause a significantly higher number of draw calls, due to allowing the user to customize their materials - with one or more surfaces per item (basically every customizable surface has its own material that the player can change, which causes its own draw call). On a mid-tier/high-end gpu, this doesn't pose much problems, and that's what I'm targeting
- The skin features options, which are overlays imposed on the character - giving you make-up and and tattoos and body hair and others - those are also adding to the number of draw calls each
- Rendering is also done in such a way to accommodate the skin features above and the additional shaders needed for generating the sweat and dirt masks, and feed them into a universal shader that takes over rendering from the regular Godot pipeline (because you can't really do these things using the default pipeline - you can do one using Overlays, but not all at the same time). You could try switching on Use legacy renderer, which gives you the pure Godot rendering pipeline, but disables all skin effects as a result.
I'm sorry it's not working ok for you, but there's not much more I can do or know how to do. If you have any sort of optimization suggestions, I'm happy to listen (although I agree that without reviewing the gfx pipeline, what I've just told you is probably not enough to go from)