Solid brick homes can be tricky. Wifi signals struggle going through many solid walls.
Some setups are:
1) Have the modem in the middle of the house, out in the open. This will spread the wifi evenly.
Re-locating the phone skt, and/or running a network cable from any NBN-NTD boxes through to another room for the the modem may be required. Moving outlets or running network cables is an account holder responsibility.
2) In very large homes, having a 2nd ''WIFI ACCESS POINT'' at the other end of a house can be beneficial. But this will also require a network cable to be run from the primary modem, to the secondary modem/access point. This is the best way for larger homes.
3) There are different types of wifi extenders. Some daisy chain wifi access points via wifi, some run over the power network. These are hit and miss in terms of performance and are the least favoured method.
Wireless interference can cause various issues with your WiFi network. If all of your devices connected to via WiFi are affected, then you may need to change some wireless settings. We've created an article that will guide you on How to improve your home network.