Modem, Without using QoS need to limit Bandwidth.

So i moved to a small town without checking ISP first. The only and fastest direct line i could get is 3mb DSL and i was told by the “Only” ISP here that they will never upgrade :/. So taking this offer because i didn’t see an option. My question is this.. Can i throttle my primary computer’s bandwidth via my Modem? It’s direct on Ethernet while my Laptop get’s VERY little bandwidth via Wifi.. I need for my Primary to stop being a Hog and for my Wireless to be able to share the connections without the interruption. I do understand that without setting up QoS “Ethernet” LAN gets te primary amount but is there anyway to stop that from happening? The little amount of Band i have is hard to work with so any Help is appreciated. Thank you for reading/Time.

Edit: to this.. If I understood my QoS settings in this Device I would use them. I have never seen anything like it before though. I have setup QoS for friends but my own is strange and Research has not helped me any.