XPS 8940, continued performance issues

I am wondering if anyone can provide some guidance on how to get a higher level of support? I have had this desktop since December 4, 2020 and have the Premium support which expires on December 10, 2021.

I have contacted support four times in this past year for slow performance issues without any long lasting results. The last time included a complete reinstall of Windows.

I can't find any way to contact anyone to try to escalate this issue. I have been a loyal Dell customer for over 15 years and never hard this much trouble with any previous desktop or laptop purchase. It is affecting my business as I sit waiting for apps and browser windows to open. How can I get anyone at Dell to take these issue seriously? 

Thanks