When you troubleshoot, if you don't know what is wrong, you can take the route of eliminating other things to narrow down the possibilities. If you put your computer on a wired connection, you would establish the system is capable of preforming the way you want. You may have some malware running in the background causing problems or something else. I can't tell you how to put your system on your wired network, but you or a friend should know.
If the system runs OK on a wired connection, then you know for sure it involves your wireless connection or some component of it.
But once you find a place when the system operates as expected, you can then build back up to where it starts having problems, then you know what is wrong...