Anyhow when I call on such I check settings and do a WiFi sweep with my android phone running "WiFi Anazlyer" (it's free) to see if the 2.4 and 5 GHz channels the router is on is not being stomped on by other routers.
In short:
1. Change WiFi channels to more open ones.
2. Use a powerline WiFi kit like this one to put a hotspot at the other area.
https://www.amazon.com/TP-Link-AV600-Powerline-WiFi-Extender/dp/B00HSQAIQU/
Example setup:
Have higher speed Internet? Consider the next faster model:
https://www.amazon.com/dp/B0725LPTZR/
Our apartment (1,000sf +/-) has plaster and lath walls. The router is at one end and the room where I work is at the other end (not an option to move router/modem). I know that I need some kind of extender, but I would like to know what I'm looking for exactly and what would be most reliable and secure). Our router/modem is from Xfinity/Comcast.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic