I had a look at a previous solution suggested on a different thread but It hasn't worked for me. I need to know if it's possible and all the steps to do it successfully.

@Marvin_S It's on auto now. This router has only 2.4Ghz . Should I leave channel and channel width on auto? Or would it be better to change?

How many devices can a TD-W9960 handle simultaneously? For some reason I can't connect to the WiFi network if it seems crowded and also it sometimes disconnects me for no reason all of the sudden...