Hi @Kayleigh . Are you using the 2.4G or 5G wifi band? The 2.4G has greater range. You can use your mobile phone to check relative signal strengths in your apartment and for networks in other apartments.
If you are on FTTB, you can use a longer telephone cord between wall socket and router to reposition the router to a better spot. (If FTTC, a longer cord between wall socket and NBN box.) Run the cord along the skirting board.
If you have NBN box, you can use a longer ethernet cable between NBN box and router.
You could consider a wifi extender if moving NBN box/router is not possible.
Some standard TPG articles:
Easy Steps to Improve Wi-Fi Connection In Your Home