Hello, I did it,
I've reactivated windows defender. And did update it's virus definition.
Tried to install 1909 ==> error 0x800f0805
Here is the new cbs.log.
And one question: could it be linked to a problem with .net framework ?
Because the only thing installed around the beginning of the problem was visual studio with it's pack of things related to .net framework.
Thanks again for your help.