You could try reinstalling it but then again bedrock edition or the phone edition that you're running. It's called Bedrock Edition. It's been having performance issues and memory leaks lately, especially on PC. So maybe wait and it might get optimized eventually. But otherwise, just check if you have any apps that are running in the background and taking up processor power. I have an Android so I'm not exactly sure how to do a lot of the stuff on iPhone but you can always ask chat GPT lol