App issues

From your Home Screen, swipe left until you get to the App Library.

Swipe downward and you'll get an alphabetical list of your apps.

Locate the app in the list or type the app name into the search field

Once you've located the app, tap/hold until it raises/selects, then drag it and it'll pop out to your Home Screen

Organize the Home Screen and App Library on your iPhone - Apple Support

It will pop out if you're doing it correctly.

Alternatively, you can find the app in the predefine categories rather than the list, tap and hold on the app icon.. it should pop up a menu and you'd select Add to Home Screen