Keep Your Apps Up to Date
If you notice your iPhone only runs slower when using a specific app, it might not be your iPhone’s fault. Maybe it’s the app that’s causing this problem.
This can happen either because of a bug in the app or because your iPhone is too slow to run the app properly.
If it’s the former, you can try fixing it by updating your app. Most developers will try to keep their apps updated so there aren’t any performance issues with them. To update your app, you can go to the App Store and tap the Search tab in the bottom right corner.
Search for the app’s name and see if there is an option to Update. If there is, tap it and wait until your iPhone installs the update.
If your iPhone is getting too old to run more modern apps, you might want to consider deleting it and finding a replacement in the app store.