Cubase 6 on High Sierra - High CPU


I was using Cubase 6.0 on Yosemite Mac OS no problem, very low CPU.

I upgraded to High Sierra Mac OS and now if I open Cubase and open no tracks Cubase is running at 17% in the Activity Monitor. If I open tunes I have done Cubase is running at near 100% or more and the fan is on max. However VST Performance is nothing and is on only 1 bar.

I have a Mac Book Pro 15 inch form Mid 2014 with 16GB ram, SSD.

If I play the tune Cubase also crashes after a while.

Does anyone know what the issue is?

Cubase 6 was simply amazing on Yosemite but I regret upgrading to High Sierra Mac OS.

I cannot make music anymore and am too skint to upgrade.

Thank you for any hints