Hi, I'm Estrella. I'll do my best to help you.
To remove that pop-up, please try the following steps:
Press Ctrl + Shift + Esc to open Task Manager. Click the 'Details' tab. Scroll down and look for the PC App Store icon(represented by an orange shopping bag; the process name may differ). Right-click on it and select 'Open File Location.' Return to Task Manager, right-click the PC App Store process again, and select 'End Task.' Go back to the folder you opened earlier and delete all files. Restart your computer and check.