[SirRickie]

when I do a fresh install of Kodi, all my scores will not be copied in the new installation (I guess that's right ?) and they all will be gone. Is there a way I can solve this ? Tnx.

Yes, quite an easy solve by exporting your video library.
This will create an NFO file for each of the movies, TV shows, episodes and music video files that details all of the information relating to video title in the library, including your ratings. Each NFO file will be placed into the source folder of your video file. When re-adding and scraping your library on a new installation, the details from these NFO files will take precedence.

Some basic things to remember when exporting:-
1) Opt for exporting into 'separate' files (This will create an individual NFO file and place it into the source folder for each of your video files, ie movie, TV show, episode etc)
2) 'No' to exporting fanart and thumbs (be careful with this one, as saying Yes will export all of the cached images on your current Kodi installation back to the source folder of the video file and these are a lot smaller in size and quality. I made this mistake once where I kept exporting artwork, ultimately resulting in very pixelated images being in my video file source folder and thus my Kodi library)
3) 'Yes' to overwrite previous files. Obviously you want your current rating edits and any other changes you make to be written to the NFO file(s).

More info about exporting the video library and NFO files can be found here:-
Import and Export library and Kodi NFO files
Hope this helps

Tnx for your reply. I will certainly give it a try.