There are several topics that affect the speed of the internet such as;
Interferences
Interference typically comes from three different sources such as; walls and floors blocking wireless signals, other WiFi networks using the same channel as your own Wi-Fi network, appliances and electronics emitting radio frequency interference.
Number of Connected Users
Your speed will be shared amongst other users, therefore the more devices connected the slower the internet will be.
Ideally the modem is not placed close to windows, or within cupboards and off enclosed shelves. Ideally the modem is placed on top of a cabinet or shelf.
Location of the Modem
Ideally the modem is not placed close to windows, or within cupboards and off enclosed shelves. Ideally the modem is placed on top of a cabinet or shelf.
2.4GHz vs 5GHz Frequencies
2.4GHz frequency is able to reach a longer distance than 5GHz. However 5 GHz frequency provides less coverage but transmits data at faster speeds.
Your Equipment
Internet speed heavily depends on your network equipment, such as network card, router or Ethernet cable.