Hi there Weismann, sorry to hear you're having trouble.
Did Slime Rancher run fine while you were running Windows 10, your post makes it unclear??
First, let's try updating your graphics card drivers.
If you have a nvidia card, you can go here:
http://www.nvidia.com/Download/index.aspx If you have an AMD card, you can go here:
http://support.amd.com/en-us/downloadThen, restart and try to launch Slime Rancher.
If that does not work, please tell us which version of DirectX you are running?
And let us know how you make out, thanks.