Force to unistall Nextcloud app in iPhone

I have installed the app on iPhone… then I uploaded the pictures on my server. Then, I accidentally delete the pictures from my server … so after that, the app in iPhone is appearing with a weird icon. I can’t open the app either. It closes automatically. I think it is something to be that the app is trying to find the pictures on the server but they are no longer there. That is causing the conflict I guess. But… i need to delete it from
The iPhone … I delete it but when I restart the phone… it is still there…
see the attached image