I assume that the complex has a shared VDSL line ?
And with poor signal, do you mean wifi signal or internet speed ?
In case of a shared VDSL line, it's main problem is the number of concurrent users..
Lets say its a 50Mbit VDSL line, and there are 10 users streaming in SD quality, it will be a "oke" experience
However if there are 20 users streaming it will need to buffer a half of the time.
The second problem comes when there is no control over the speed per user, a single user could take more then a fair share of the speed
For example, if 1 user is downloading movies via torrent, this could eat up the entire 50Mbit.
Another problem can be mobile phones who upload the photo's and video's to the cloud, this can take the entire upspeed of a vdsl line.
When the upspeed is fully taken, all other internet services become slower as they have to send out a message to the server to receive the next package.
I have seen several locations where people where very happy with the shared internet until several tv stations were lost from the sat dish.
They then started to stream. The load on the connection became so high that many started to complain.
After having a closer look, i noticed several users who left the streaming box on and just simply closed the tv. So in the background the box was still streaming and taking bandwidth that was not needed. Educating the clients helped a lot in that case.
Most people now consider and use the shared connection with respect to the others.
In several hotels i placed a second line (sometimes even 4 lines) to catch up with the higher demand of the clients.
There are clients who do more then 50GB in a single week of holidays ! (i wonder if they ever leave the room)
Also i limited the clients to either 5 or 7Mbit per device to stop a single users of using all the internet.
So it greatly depends on the number of users who are there online and what they are doing, plus if there is any control over them.
Regarding poor wifi reception, depending on the setup, it might improve when you install a repeater router in your apartment.
Wifi needs a proper setup because 1 single low connection will bring down the speed of all others, even when you stand next to the router.
Lets say there is one apartment on the edge of the wifi signal and he can just connect to it. The router then must do its best to provide network to that client. But because of the poor signal, the router might need to repeat the send messages many times. This takes time and all other clients get less time (speed). So there should be enough routers in the complex to give each apartment proper signal. This will improve speed (up to the max of the line of course)
Everything greatly depends on the setup in the complex, so if you have more information it will help to get a better advice.