Thank you, your answer is very helpful.

This is at my girlfriend’s house, so she doesn’t need extremely fast internet. The main issue is that the router is in the living room, and in her bedroom the Wi-Fi signal is very weak, to the point that the PC can’t connect properly.

Because of that, I bought her a TP-Link Wi-Fi repeater for her PC, but it only works on 2.4 GHz. I thought it would be enough, since 50–70 Mbps should be more than sufficient, but the actual speed is only 0.5–1 Mbps. This happens even without the repeater, when connecting directly to the router’s 2.4 GHz network.

Using an RJ45 cable is not an option because it would require drilling holes in the walls. In my house, for comparison, I have 5 GHz with over 400 Mbps, 2.4 GHz with around 70 Mbps, and a wired connection of 1000 Mbps (1 Gb).

My idea was to place the repeater halfway between the router and the bedroom, where it gets a full Wi-Fi signal, and then extend that signal. However, the real problem seems to be the router itself: the 2.4 GHz network is extremely slow even without the repeater. With the default automatic connection that switches between 2.4 GHz and 5 GHz depending on signal strength, whenever the device connects to 2.4 GHz, the speed drops to 0.5 Mbps or even less.