Zoran, in case you still don't understand what he is saying, what you download from Apple is an application bundle. You cannot boot your system from an application bundle, even if it is an installer. You need to have an installed system somewhere to boot from. That is, why for example, those of us who have unsupported Macs, have to take that installer app, use a patch, and install the system that the installer app contains on a flash drive or external drive or partition, and then from there, use that to install the system on our machine's internal hard drive. That is precisely what
prisstratton is telling you to do, using diskmakerx. In other words, you need to actually install the system that the installer app contains on the partition that you mentioned.