@Jalen217 

This is normal. Satellite Deco that is wirelessly connects to Main Deco will cut Main Deco bandwidth by half. This is not Deco mesh problem, this is limitation of technology. Any other WiFi mesh brand will have the same.

Satellite Deco is an intelligent range extender. They both run on same physical principles. Because of that, to find more detailed explanation of why Satellite Deco is slower than Main Deco, Google "WiFi range extender cuts bandwidth by half." What discussed there is applicable to Deco mesh, and to any other WiFi mesh.