"So I uninstalled LR6 and installed it again with my CD on my Windows 10 laptop."
You probably don't have the latest version of LR 6 (6.14). Others have reported that earlier versions of LR 6 have started crashing on startup. There is a newer version of LR 6 available, LR 6.14. Others have recently reported that updating to LR 6.14 fixed crashing-on-startup problems. Try installing 6.14, which you can download following these instructions: