Agreed with FusionXY, repeater is a bad idea with the existing router.
First, wifi speed reduced more than half and including ping speed which affect gaming alot.
2ndly, if you move around the house, it does not support fast change or roaming over like mesh router, let you connecting to wrong router when you are in a wrong area.
Ofcourse for speed, you can pull a Lan cable connecting to the repeated or like I do here, connecting to Time Tplink AC1200 as AP router.
I'm happy with my setup now, in living room and master bedroom, my phone can achieve 4XX mbps and 2nd &3rd bedroom is around 3XX mbps on Time 500mbps package.
I stay in condo around 1075 sqft, due congestion in 2.4 ghz and also 3 thick walls between 2nd and 3rd room resolve into 2nd router.
If a good router can reach behind those walls, I will rather use high-end router like FusionXY suggested.
For my case, I know it won't be as good having a cheap 2nd AP.
To have better mobility between the router, I have setup my 2nd router with different SSID so I know if I'm connected to wrong router.
So far it switch nicely 80% of the time and this is something I may want to improve in the future with mesh capability.