Imagine that the expander model re605 v1 gave me a better result than the re505x

Is it better to enable this option Band Steering or does it make no difference?

I am having a lot of trouble with this modem to connect it to the extender I tried four types of extenders and the result is very bad

Are there any other settings that can solve the problem?

I did as you told me. I put the extender next to the router, almost at zero distance. The percentage still does not exceed 70 percent.

What is half-duplex? Is it an option that can be disabled? Excuse me, I am new to this field