Q: BootCamp Install button is greyed out

I need to install a Windows 7 on my MacBookPro but the installation button is actually greyed out.

I first managed to install a first windows but i needed it to be bigger, so i deleted the BootCamp partition with a live GParted USB and here it is, impossible to get this again.

Here are the `diskutil list` and `diskutil cs list`

And here is what my disk looks like actually

Please help me, i don't know what to do ... I got a live USB of GParted if needed.

Thanks in advance !

PS: I'm on a MacBook Pro (Retina, 13-inch, Mid 2014), with Yosemite 10.10.5