Hi leptoon,
I hope I can help you here, sorry to see you're having a bad experience with this. You can try specifying a new directory in the Registry Editor, though it's no easy fix, but I'm here to make it at least a little easier by guiding you through it.
Hit Windows key + R together and enter: regedit
In the new Registry Editor window, navigate to the following: Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Appx
Right-click that Appx folder, then click Permissions... in the context menu, then click Advanced. Change the owner to your name. Enter your user name in the box under "Enter the object name to select", then click Check names. Once your name has been verified, click OK. Make sure that "Replace all child object permission entries with inheritable permission entries from this object" is checked, as well as "Replace owner on subcontainers and objects." Click OK again.
Make sure that the Administrators and Users groups have full access. Now change the value of the PackageRoot entry on the right pane, to the directory you want to set it to.
Reboot if you have to, but this might work without it. I hope this helps. If this didn't work or if this worked, I'd like to hear about it. Let me know.