HOW to update CUBASE 8.5 to 9.5 on Win

I bought the update only as I already have the 8.5, but the steinberg assistant downloader only give to me the FULL 9.5 installer and not only the update/upgrade that doenst seem to exist.
How do I proceed ?
Im always afraid to lose some datas or to have unstable system if I do it in the wrong way.

Many thx

You have to download the full installer. The full installer always comes with all of the factory content , and will update any components that are already present in your system.

Further to RTp’s comments, 9.5 is a completely new program and will be installed alongside your copy of 8.5.
This is to your advantage and I strongly advise you to leave the 8.5 program in place until you’re happy with everything about 9.5.