Uninstalled apps on iPhone still show up in Settings iPhone 8+ iOS 13.5.1
I deleted the app and it still shows up in Settings, so I could not re-download it again. In the App Store, the app just says Open.
I’ve tried shutting it down multiple times (didn’t work).The app is grey with lines and it’s Snapchat.
How can I remove it from Settings?
To expand on my comment. Often these kind of issues respond to the backup, wipe, restore process. Here it is in greater detail

Plug your iPhone (or iPad) into your computer, launch iTunes and select the option to back up your device locally (rather than iCloud)
IMPORTANT Set a password for the backup. That will ensure the backup preserves all saved passwords. you will need to remember your AppleID password and unlock PIN.
Once the backup has completed, go into iCloud and turn off Find My iPhone, and unplug the phone from your computer.
Go to Settings &gt; General &gt; Reset and tap on Erase all contents and settings. you will be asked to confirm. Do so. The reset will take a few minutes. When it is done the iPhone will be at the setup screen, just like when you bought your phone.
Early in the setup process you will be given the option to restore from backup. Choose that, plug your phone into the computer and proceed with the restore.
When the restore is done the phone will reboot and proceed to download all your Apps. Unfortunately Apps are no longer stored on the computer during a backup so they all have to download, this may take a while depending on how fast your internet connection is.

When that is done you will have a freshly restored iPhone, identical, in configuration and settings as it was before. you will have to re-enter your AppleID and AppleID password but everything should still be there.
Note that doing this will usually clear temporary/deleted files that are otherwise not deletable, clearing usable space on your iOS device. It will also solve a lot of issues with the phone acting strangely and apps not working correctly, as well as the ghost app icons sometimes seen.