A couple of things. Can you give a FULL disk management screenshot that shows partition size info. Also some english translation.
What do you really want to do with a clean install? Normally people do this when they want to get rid of the OEM (ASUS) material and start from scratch. Of course you need the drivers
so see what ASUS have to say. You can send the screen shot - what drivers are you missing?
Also, ask them what factory restore
DVDs would cost just in case you may need them.