Is my iPhone affected by amount of downloads?

My iPhone seems to run slow and also sometimes when I click an app to open it will just close back to my home screen. What's going on? How do I fix this? Is it recommended to completely reset my device?

The black one runs faster

Usually if an app just closes to the home screen it means you need to update your apps, go to the App Store and press 'update' then update any apps that need updating, hope thi helps

If you have to many apps its slows down your phone.