Samsung S21 FE Lag, Screen Burn & No Suppor

I purchased the S21 FE around nine months ago, and unfortunately, it has not lived up to my expectations. The games have a significant lag issue, to the point where even my brother's A03 performs better. I've noticed screen burn-in on my device, even though I haven't done anything to cause it. I've reached out to Samsung multiple times via phone calls and written complaints, but unfortunately, they have not provided any resolutions. I am disappointed with my purchase of this phone.
Adding to the frustration, I even went ahead and got Samsung Care+, hoping for a resolution. However, despite countless calls and detailed explanations of the problems, the issues remain unresolved. I'm incredibly annoyed that I've stashed the phone back in its box and resorted to using my old phone once more.
I require a resolution, please. It's frustrating to invest a significant amount of money in a device that has such subpar performance. I'm contacting you again, for the fifth time. If there's no resolution this time, I'll take the necessary steps to address the issue.