Question ISP Modem + Access Point + Switch = Slow Connection


Aug 13, 2016
Hi everyone.
I don't know much about networks so this issue might look kind of dumb to some of you, but I recently upgraded my internet speeds from 100Mbps to 300Mbps and can't seem to get those 300Mbps on my main PC.
On the ground floor of my apartment I have the ISP's Router (Sagemcom F@ST 3486AC), which is connected to a Gigabit Router (TP-Link Archer C7) acting as an Access Point on my first floor. In my room (first floor also) I have a Gigabit Switch (TP-Link TL-SG108) hooked to the first floor Router, which feeds two Windows 10 PCs.
(Here's a little diagram of what that looks like

Leaving each connection as is, I only get 100Mbps speeds on both PCs, but here's where it gets interesting: If I remove either or both the TP-Link Router or Switch from the equation I get 300Mbps. I also noticed that the switch recognizes my ISP's Router connection as a Gigabit Connection (green light) but not the TP-Link Router's (amber light).
I tried configuring the Switch with the Easy Smart Switch tool but it's not even able to find the switch in my network.

I should also mention that, when going into the Access Point's settings, I saw how it identifies what's connected to it:
This is with the Ethernet Switch connected to LAN2, showing up as a 100Mbps connection.
This is when I connect either PC directly to the Access Point, without de Switch.

Does anybody know why this might be happening?
Thanks in advance!