LAN Bottlenecks effecting Wireguard performance

I currently reside in Vietnam using GL-MT300N-V2-a55 Mango Router to connect to a Mullvad Wireguard VPN server in London UK.

I am unsure of the best way to set up the router to get the best performance. My main problem is that the upload speed a severely restricted (getting speeds of 0.2MB). The download is OK around 15MB.

I believe the problem is something to do with how the local network is set up which is causing a bottleneck. The network has a WAN router downstairs and 2 WIFI networks around the house configured as repeaters.

If I connect the Mango WAN port directly to the WAN router and then plug my laptop directly into the router with a cable I get great performance 25 Up 25 down.

The problem is my desk and chair are located upstairs and WAN router is downstairs. The WIFI works fine upstairs without the Mango and VPN. How can I set up the Mango upstairs so I don’t need to plug it directly into the cable?

You can test the speed of connecting the Mango WAN port to the WAN router downstairs, then connecting your laptop upstairs to the Mango WLAN wifi.

I do not work for and I do not have formal association with GL.iNet.

I tried that. It was working yesterday with the cable and then it stopped working again. I am getting inconsistent results here are some tests performed yesterday:

Mando router cable plugged into to viettell repeater downstairs
laptop connected via cable run through wall
DOWNLOAD
0.22
Mbps UPLOAD
5.74
Mango router plugged into cable to WAN Router downstairs
laptop connected via WIFI
DOWNLOAD Mbps
16.18
UPLOAD Mbps
0.23

Mango router plugged into cable to WAN Router downstairs
laptop connected via cable downstairs
DOWNLOAD Mbps
25.59
UPLOAD Mbps
25.02

Mango router plugged into cable to WAN Router downstairs
laptop connected via cable through wall
DOWNLOAD Mbps
0.10
UPLOAD Mbps
5.88

Mango router plugged via cable to WAN Router downstairs through the wall
laptop connected via WIFI
DOWNLOAD Mbps
15.36
UPLOAD Mbps
0.25

Mango router plugged into cable to WAN Router downstairs through the wall
laptop connected via cable
DOWNLOAD Mbps
0.07
UPLOAD Mbps
13.42
Mango router WIFI to Bi Do SSID
Laptop cable
DOWNLOAD Mbps
0.03
UPLOAD Mbps
15.38

I just retested again. Connected the Mango WAN port to the LAN port on the WAN router then connected my laptop to the Mango WIFI upstairs. The WIFI kept dropping so I couldn’t even complete the test. I am now sat a few metres from the Mango and I get these results:

DOWNLOAD Mbps
1.21
UPLOAD Mbps
0.14
Ping ms 229 191 185

Ok, so the bottleneck does appear to be the Mango. I’ve switched off VPN completely now for testing. If I connect the Mango WAN port to the WAN router LAN and then connect my laptop to the Mango LAN with a cable I get the following:
DOWNLOAD Mbps
1.31
UPLOAD Mbps
93.66
If I then connect my laptop directly to the WAN router with no Mango I get:

DOWNLOAD Mbps
94.53
UPLOAD Mbps
94.27

Thinking maybe I need to reset the Mango and start again or maybe it’s faulty hardware?