I just tried making a TIFF with transparency, and importing it into Earth did not show the transparency. Saving it as a PNG did keep the transparency..
I see but what if you try with the original image? You can download from with the link beneath, if you cant to.
Beacuse of the data laying in the image I cant just turn it into a PNG, because then these data about the pictures location in earth will be gone?
Would it be too much to ask, if you would tell exactly how you did it, from when you downloaded it and until it looked like the picture you posted?
I'm not sure how to "save with Transparency", as I can't seem to find a place where that's possible
After I downloaded your TIFF, I added it as an image overlay in Earth. The version of Earth I have been using is an older version that does not have the 'Import' function. It opened with transparency, and centered on the screen, not using any location information. I then opened it in some GIS software, which did retain the location, but only 1-bit transparency (sort of like a GIF).
A number of Google searches for various combinations of "TIFF", "GeoTIFF", "Transparency", and "Google Earth" didn't give as much information about GeoTIFFs as I was hoping, but I did see lots of references to "Google Earth Pro", so I installed that. I imported the TIFF, and it opened in the proper location as seen in my screen shot, complete with a full range of transparency.
The Save with Transparency is in the TIFF Options dialog that comes up when you save as a TIFF:
When I re-saved the TIFF I had made with this box checked, it appeared with full transparency in Earth.