I'm facing an issue of slower than anticipated internet speed with my computer which is connected to a Deco.
Some info about my setup: 

Internet connection is 350 download / 35 upload.

I have connected the main Deco to my modem/router (which is far away from my computer) and have connected 2 other decos to the network.
While using WiFi my internet speed is high (>320M) wherever I am in the apartment.
I have now connected my computer via ethernet cable (5e) to one of the secondary decos, since my modem/router is very far away so I can't connect my computer there via cable.
The internet speed on my computer cannot exceed 100M, while my phone (I can see from the app that it's connected to the same Deco since it's the closest one) has full speed.
The ethernet port on my computer is 2,5G.

What might be the problem with that?

Thank you