1.18 mob spawning lag in Minecraft PE

I already made a new world. I started it right away, I went into a giant cave.
After I went to a giant cave, there is lag because of double the mob spawning.
I played Minecraft is less than half an hour (20 minutes), and all of the mob movement was too slow and I can't open the inventory menu. Once after 25 seconds it's back on.
IDK why but the mob spawning, it's so deadly. Mojang, please fix this issue because I couldn't handle my phone this much, even in low settings.
I will send a video later and I forgot to record it when I got this bug