Why os loading slow amf cant delete things or downloading

Pop up is virus in system. Fooling you into downloading the rest of itself.

The only way to remove it from your phone is to reset your phone.

1. Backup all your photos. Do not connect your phone to your PC to backup your phone as the malware may transfer over to your PC! Use Google photos to sync your photos to the cloud.
2. Backup any other data using other cloud services.
3. Reset your phone. Go to backup and reset in settings, and reset your phone.
4. If the reset still doesn't fix it, use Malwarebytes from the play store to scan your phone. This probably won't help if a system reset didn't.

Hope this helps!