laggy freezing premiere

Specs first off are:

Mid 2015 Macbook 15 inch

2.2 Ghz I7 core

16gb of ram

graphics: intel iris pro1536mb

250gb of storage 

I stopped doing videos around 2017

its 2019 and im back in it and my computer cant seem to keep up with premiere

it used to have the fan running back in the day but other than that it ran smoothly

now its slow and glitchy even after i render it.

the footage is 4k ( i know 32gbs of ram is recommended) but i proxied them to a lower quality and its still an issue.

Any help? im currently scanning my computer for viruses just incase theres something there