Adobe applications - Case-sensitive volumes not supported I need someone to put this together in the most fool-proof way possible.

I recently reinstalled the OS on my Macbook Air 2014 (Yosemite) as I had a ton of useless files as it was acting super duper slow so now that I want to install Photoshop, Illustrator and InDesign (which my entire life depends on as I'm a design student) it gives me an error: 
Installation on case-sensitive volumes is not supported. Please choose a different volume for installation.

I know this topic has been discussed before but tbh I didn't understand a thing going through them lol. So I know there is this thing called iPartition but I currently don't want to spend any money on apps and am more than happy to reboot my entire Macbook or pick a different OS if that helps. 

Any thoughts?
Here's what Adobe has to say about this error. 

It means you have to reinstall OS X. 


Reformat and Choose OS X Extended (Journaled) as in the image above.