I had the Debian 9 installed on an Acer M.2 NVME disc, but I had problems with the keyboard in Spanish, since I used es_ES.UTF-8 but we were unable to remove the default configuration C.UTF-8, since it did not I know if it is the cause of the problem.
I can't delete C.UTF-8
You don’t have to delete C.UTF-8. It doesn’t matter.
You should edit the /etc/default/keyboard file.