How setup Queue limit at this network 3WAN to MikritikRouter to 3switch

I have two problem needed to solve here

  1. How to limit internet access speed, i know use Queue, but add all ip staff pc, then many pc access internet starting slow
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  2. there are about 40 pc at 3 switch use one cat5 cable(look at the redline) connect to router, want i need change cat5 to cat6 cable?
    Because network starting slow if many pc access HDD server(many time) and printer and again access internet