I purchased 2 x cpe 510 to get wifi from my house to my garden office.

I have a fritzbox router and 1 x fritzbox repeater in mesh network.

I first tested the cpe510 as a 2nd repeater to make sure it gave good speed, and it didn't, it was awful.

I assume the cpe510 was connecting to the fritzbox repeater, a that was closest.
If I speedtest using phone from the same room I get over 300mbps from my fritzbox repeater.

If I enable the cpe510 and do the same test, I get about 12mbps

Connecting the cpe510 to the fritzbox repeater via ethernet doesn't;t help, in fact this kills my internet connection. I only seem to be able to connect it via wifi.

So then I tried setting up as a bridge, and the 2nd device as client.
This did improve this, as I am about to get about 50MB from my office, with line of sight and nothing the waym  but I expected it to be better.

From just outside my office I am able to get about 100mbps from the fritzbox alone with a speed test on my phone. But alas the signal won't quite make it to inside the office.
And this is with a brick wall between me and fritzbox, thus why I expected better from the CPE510, with line of sight and no walls.
 

The distance from the house to the office is about 20 metres.

Am I missing something here ?

Does spe510 really not support a wired connection for the bridge device?