Okay, I see. Please confirm the permission for plugins deactivation and switching to the parent/default theme for testing. Also, send me access to the admin panel.
On the default theme, we can see that the page loads more than 3s – https://prnt.sc/uBPBaKVcUdku , if we disable 3rd party plugins it will be around 1.6s – https://prnt.sc/HfddXofI9f-c which still not the best result as the default theme should be loaded around 1s. Therefore, we can see that the speed affects by 3rd party plugins and not stable server.