I'm stuck connected to the farthest wi-fi booster

[wireless]

I often find my cell phone stuck connected to the wi-fi booster on the 2nd floor in my house. When it does, my download speed only gets around +8Mbps. To fix it, I would turn off my wi-fi on my phone. Then stand next to the wi-fi booster that is located on the main floor, and turn on my wi-fi. Once connected, I would get +100Mbps on download.
I thought a mesh network is supposed to choose the fastest connection. Why is it not doing that for the TELUS Boost Wi-Fi.

My wi-fi booster are both connected by wire.

Please help, thanks!

More...