Internet speed has dropped wildly, what should I do?

Question

Computer networks

Greetings, the essence of the problem is this, on the old computer the Internet speed was normal, downloading anything through a browser or torrent was no problem. I COMPLETELY updated the computer and the speed of the Internet dropped to 1 MB, either from the browser or from the torrent, I sinned on the router, but I don’t know how to change the settings in it, I already searched everything, I don’t know what the reason is, I called the provider, they are all nishtyak and the speed is not cut. Tell me how to be????