@Emjaaaay your speed is indeed low. I think the issue is within the physical side of the network like the cables outside, equipment, etc.
Just out of curiousity, do you have a landline that you can plug in on the phone socket to test if there is dial tone or if you can make and receive calls?
On most circumstances I would recommend the contents of this article https://community.tpg.com.au/t5/Featured-Articles/Troubleshooting-a-Slow-Internet-Connection/ba-p/11...
I think your issue is related to a phone problem, please remember that any issue on the phone service will definitely affect the internet.