What happens if you go to this page:
then scroll down the page, and select the French/Pro 2019/Windows download [Télécharger][https://www.sketchup.com/sketchup/2019/SketchUpPro-fr-exe](French installer, SU 2019 Pro/Windows) link?
When I do that, I download a file called SketchUpPro-2019-fr.exe.
Did you get that? And if you install it, does it install in French or English?
Remember to right click and select ‘Run as Administrator’ or the French equivalent.