So, sda has sda1 (windows), free space 314GB and sda2 ntfs. I should choose free space and create 2 logical partitions (swap and /)? I did this but then nothing booted...
Thank you for replies!
Edit: Now I do it again: In free space above I created e logical partitions sda5 for / ext4 287GB, sda6 ext4 for /home 20GB and sda7 for swap 6GB. I chose device for boot loader sda5. Let's see what happens..
Flip the sizes around. Root(/) only needs to be 20GB, but your home partition where you'll store your personal files should be large.