Hosting a server and playing at the same time

I'm trying to host and play at the same time. Currently it runs about 40 ticks behind when I host and play with 1 other friend.

I have it set to run with 8gb of ram, however it is my cpu that is the problem I think.

I use an i7-8700k and have a total of 16gb of ram. Any suggestions would be great thanks.