Zombie App won’t delete or reinstall

How do I completely eradicate the traces of an app from my IPhone?

I have an IPhone 6 with IOS 11.4.1 and recently I’ve had an issue with a specific app. Snapchat, in fact. It’s been glitching terribly so I tried fixing it by deleting it from my home screen and reinstalling it a few times and now it won’t leave. What I mean by that is that it appeared as a grey-ish-white-ish app icon with lines crisscrossing it out of nowhere after I tried deleting it for the umpteenth time from my home screen. Each time I keep restarting my phone using the home button and off/on button again and again after that it STILL reappears! In the App Store, I checked it and it said ‘open’ as if the app was completely fine and working great, but NOTHING HAPPENED when I pressed on ‘Open’ over and over again. My blood was boiling⬇️+

Anyway, once the home button/sleep button restart thing got tiring I took to ‘Settings>General>IPhone Storage’ to try deleting it from there and discovered an even bigger issue. It really was stuck on my phone. Snapchat was in my IPhone’s storage taking up unnecessary space and being completely useless. When I attempted to press ‘Delete’ or even ‘Offload’ it would simply disappear for a moment from the list of apps in my IPhone storage before IMMEDIATELY reappearing before I could even exit my Settings app. It even says ‘last used August 14th’ even though I haven’t been able to communicate with my friends since yesterday because this app decided to be terrible at deleting itself. +

So, tldr: I have no idea what’s going on with my phone and I’m a little scared and a lot worried right now. I’ve tried every trick and all steps I’ve seen on the internet to get Snapchat to quit haunting me, but nothing’s worked. I even tried deleting its backups from ‘Settings>Name>ICloud>Manage Storage>Backups>This iPhone’ because apparently that aids in deleting it wholly but it literally said ‘No data.’

Please help me. I’m too scared to do a factory reset because I don’t know what data will and won’t be saved from my phone if I backup and 100% restart my iPhone for the sake of one petty app. I don’t have iTunes and I’m just so, so exhausted.

Tell me, please, is there any other way for me to fix this? :(