My main deco connects the satellite deco by wifi. Why the satellite deco gets a speed about 15% faster than the main deco?

When my samsung galaxy s20fe is connected to xe75 ,it always connects to 2.4g. It does not switch to 5g although I put it near the main station

Should I use straight through or crossover cable to connect 2 deco in ethernet backhual mode

I connect my client deco xe75 with the main deco xe75 via a switch in ethernet backhaul Can I link up the client deco with a desktop pc by lan cable and will the pc enjoy the full speed of ISP provide