How to manually partition a hard drive for two Linux OSes?

Question

linux

Good afternoon.
On a working computer there was obligatory ROSA Linux. Since it is completely dead and nothing is updated, it was decided to install a fresh CentOS, which was done.
But for some reason, I thought that there would be something similar when installing Linux parallel to Windows, when the bootloader sees both OSes.

In general, I attach a photo of what is now on the disk.
And here, as I understand it, you need to edit grub with your hands, but I generally wanted to demolish the / dev / reld partitions, but I don’t understand at all how to do it with regular CentOS tools, so that later I can put Rosa in the unallocated area.
The main question is: how to do everything correctly so that you can roughly see both OSes?

Answer 1

Setting Up grub2 on CentOS 7

Answer 2

sudo update-grub