Shutdown unneeded services to free up RAM as CSGO lives in RAM. Us blackvipers safe desktop to disable those you dont use.
http://www.blackviper.com/service-configurations/black-vipers-windows-10-service-configurations/
Optimize steam by reducing the friend and ingame options that take performance.
Optimize CSGO settings using and be sure to use most of number 4 in the link.
https://www.esportsettings.com/csgo-optimization-guide/