Cubase 9 crash on osx 10.11

hi I’m Ivan from milan I’ll explain my problem:

have mac osx 10.11 el capitan (i5, 8 gb ram, 250 giga hard disk)

d.a.w. cubase 9 pro, and steinberg ur 44c.

Cubase works me jerky it’s been slow for 2 days

I tried to disconnect the sound card and only work with the internal one but it’s slow the same

They told me that your 44c hasn’t gone with osx10.11, but I’ve been using ur44c with osx10.11 for 2 years now

And a sound card problem ( I know your 44c is not compatible with osx10.11 but I have been using it for 2 years now)?

And a cubase problem? and if you what should I do

I need to upgrade osx 10.11 to a newer version

Thank you for your answer