Chuwi Hi12 reinstall

I want to reinstall my older, dual boot, Hi12, Can anyone provide me the active download links & the Howto ??
searched the forum several times but cannot find for z8300 where the download links are active
Serial Hi12 Q64G45160506446
thnx in advance

please use this one:

Thnx for the very quick response, i’m trying to download the 3rd part but there is a download error. .
can you look into it. “Generating new download key”Screenshot at 2019-12-26 06-28-53
Could you also point me to a howto and a android download to do a complete reinstall??