Hi MakMo. I'm Greg, 10 years awarded Windows MVP, specializing in Installation, Performance, Troubleshooting and Activation, here to help you.
It's good to pare down apps and other content you don't want, but by no means is it sure this is the cause of a slow PC. So after we fix the uninstall issue I'll help you investigate further what the problem might actually be.
- The error is a Store error. Are you having problems playing games or installing apps/games in the Microsoft Store? If so I can help you repair it which is what normally solves that error.
You should be uninstalling Apps in Windows Settings > Apps > Apps & Features. If Apps won't uninstall there then try in Safe Mode with Networking (so you have internet), or Safe Mode, accessed by one of these methods: https://www.digitalcitizen.life/4-ways-boot-saf...
If that doesn't work then try these alternatives:
https://www.tenforums.com/tutorials/4689-uninst...
http://www.thewindowsclub.com/uninstall-windows...
https://www.pcmag.com/how-to/how-to-uninstall-p...
https://windowsreport.com/remove-stubborn-softw... (Avoid ad links which intrude into editorial copy, especially avoid Restoro and Reimage ads)
https://www.dell.com/support/kbdoc/en-us/000137...
https://appuals.com/how-to-uninstall-programs-o... (Avoid ad links which intrude into editorial copy, especially avoid Restoro and Reimage ads)
- To find and fix problems go over Windows using this checklist to make sure the install is set up correctly, optimized for best performance, and any needed repairs get done: http://answers.microsoft.com/en-us/windows/wiki...
Start with Step 4 to turn off Startup freeloaders which can conflict and cause issues, then Step 7 to check for infection the most thorough way, then step 10 to check for damaged System Files, and also Step 16 to test a new Local Admin account. Then continue with the other steps to go over your install most thoroughly.
- Update your drivers and BIOS/UEFI firmware from PC or motherboard maker's Support Downloads web page, using the full model number, Serial Number or Dell Service Tag on sticker. Compare the latest drivers available for download with the ones presently installed in Device Manager reached by right clicking the Start button. Make sure you have the latest BIOS or UEFI firmware, Chipset, Display (Video), Sound, USB3, Bluetooth, Network and all other drivers, or else download and install the latest now.
Updating drivers from the Device Manager or Windows Update is rarely enough. The most basic thing we need to learn to maintain a PC is keep the latest manufacturer's drivers installed from their Support Downloads web page.
- If nothing else works then do a Repair Install, by installing Media Creation Tool, open tool and choose to Upgrade Now. This reinstalls Windows while keeping files, programs and most settings in place, is the most stable method to advance to the latest version, and solves most problems. Tutorial here: https://www.tomshardware.com/how-to/fix-windows...
Based on the results you post back I may have other suggestions if necessary.
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Standard Disclaimer: There are links to non-Microsoft websites. The pages appear to be providing accurate, safe information. Watch out for ads on the sites that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the sites before you decide to download and install it.