app store

Last Troubleshooting step: something could have gone wrong during your last update.

To install a fresh copy of your latest iOS (keeping that AppStore is a "built-in" app, included in iOS), create a full backup of your device, then restore it to factory settings, and, in the end, set it up as new:

Restore your iPhone, iPad, or iPod to factory settings - Apple Support

When done, test it for a while, without restoring data.

If the AppStore is okay, restore your data from your previously made backup.

Regards

Giulio

Force restart your iphone 7: Press and hold both the Side (or Top) button and the Volume Down button for at least 10 seconds, until you see the Apple logo. When it appears, release both buttons, wait for your iphone to restart, then test it.

Regards

Giulio

Check if you have restrictions enabled going to:

Settings>Screentime>Content&Privacy restrictions>Itunes&AppStore Purchases... the first 3 options must be "allowed".

Regards

Giulio

Are you using Wifi network? Are you sure that, for example, Safari and/or Youtube can navigate on internet?

Giulio