UE 5.4 - Extremely poor performance on Mobile

Hello, how are you?
I’ve been struggling with many things regarding the development of Unreal for mobile devices for a while. Both with the high weight of the games, and common problems.

A while ago I paid for the Google Play developer license to upload my game. And when I tried to upload it I was forced to update my project to version 5 of Unreal. (Before my project was at 4.26) due to some problems and Google Play issues, I think.

The thing is that in version 4.26, my game had excellent performance. Very bad cell phones like my parents’, who struggle to run the YouTube application, had excellent performance with my game. Mine had 60 fps without decreasing at any time. And my parents’ had the same performance, maybe they dropped a little from time to time. But they had excellent performance.
But now that I migrated to Unreal 5.4 to be able to publish my game on Google Play, I can’t help but notice that the performance has plummeted. My phone, which had a solid fps, now struggles to reach 30 fps. It’s obvious that there’s something strange in Unreal 5, because it tries to stay at 60fps but it jerks below 30fps. Now, let’s not even talk about my parents’ problems. I can barely open the game and if I manage to exit my main menu, the game closes before loading anything.

I’m like crazy fiddling with the performance settings, but I can’t get the performance to improve. I have to reduce the resolution scale to less than half so that the performance is at 60fps. So clearly there’s something strange in these versions of Unreal.

So I want to ask, do you have the same problem? And how are you solving it? I don’t want to go back to 4.26, because I’ve already done a lot of things in version 5, and I don’t know if it’s possible to migrate back. I also don’t know how to get around Google Play problems again.

Edit: I want to take this moment to add a problem that I also have just for migrating to UE 5.4
My Landscape on Editor


My Landscape Final Result

where there is originally shadow, it is vaguely illuminated, and where it is illuminated, it is filled with shadow.
As if my light texture were upside down.
This terrain looked good in 4.26, but if you’re wondering how the material is made, it looks like this:

nothing???