As Dave advised, image burn is typically not covered under the manufacturers warranty, as it is a sign of miss-use of the product and generally considered wear and tear/user fault. However, I'm happy to look into it and discuss with the manufacturer Waveshare for you, and we'll do what we can to help.
So, lets start again.
Could you please send an image of how the screen is behaving?
The screen is on for a few minutes, then whatever is on the display permanently "burns" itself into the image? Then once you unplug the device from the power and re-power the image is still the same, and you have to wait days for it to "reset"?
I've done some research, and this should be fixable. You need to use a Windows PC and plug in the monitor:
Please install this Static Screensaver
. And please swap the Static Colour to Black & Background Colour to White, like in the picture below, and leave it to run on the screen overnight.
^^ Please let me know if that fixes the issue?
For your reference, if the product was not functioning correctly after 1 month of use you really should have reported it then. Continuing to use the product up to 15 days before the warranty expires, and then requesting a replacement is cutting it a bit fine