Can anynone help me?

since I restarted my cell phone, when I'm outside the room where the router is, I have a signal, ie. wifi/ internet but when I'm in the same room it's even worse when I'm near the router I don't have internet maybe I have 2 minutes and it goes off then I have to go to my mobile phone again and search for the network, please help me because I don't know if it's connected to the mobile phone or the router can be used by all the other residents, only me doesn't want to catch the internet in the back room, help me