Ok, I have an external Hard Drive, I already format it and I have some files in it, I want to divide the Hard Drive into two different partitions, can I do it without losing any of the data I have in it? and also what happens if I select Mark Partition as Active?

Thank You.

Marking a partition as active makes it the drives bootable partition. Each drive can only have one active partition.

Unfortunately, Windows doesn't come with any tools that can resize partitions without first removing the ones that exist. There are good third-party tools that allow you to resize partitions without recreating them. My personal favorite is Partition Magic. These tools often times cost money, but there are free alternatives. If you really want to use a free alternative, then I'd recommend NTFSResize. Read the FAQ question "How to resize NTFS without data loss?" for more information.