Can't resize partition?

I went to disk utility to resize mt primary partition (to extend my BOOTCAMP partition) and I realise that I cannot resize it. I was able to resize it before, but after using MiniTool Partition Manager on Windows, I can no longer resize my primary one. Here's an image:

I should also mention that when I open iPartition by Coriolis Systems, It gives me an error message saying:

You cannot make changes to the disk from which your system booted.

To make changes to this disk, you should either boot from an external drive, use Target Disk Mode with another Mac, or create a boot disk.

You can create a boot disk by selecting “Create Boot Disk…” from the iPartition menu.

(sorry that I closed my older post, I made a colossal error)