Mac mini makes my network slow

My mac mini makes my network go really slow when its connected, I turn it off and the network preforms properly. I have changed DNS and nothing changed, I have started in safe more and nothing changed. I have run virus software and it still does it. I could really use some help here, because I have business that I need my computer for. Thank you in advance

Oh also I have 2 iPhones one mac laptop as well as another PC laptop and desktop on the system, not all of them are running at the same time though.

I live out in the country and on a good day I get:

2.8 down

.7 up

and between 70-95ms

If there are any other questions please let me know I will answer them as quickly as possible

Not exactly sure what operateing system, though I do know I have done the latest update

Thank you