
why has the font of my terminal been changed?
It's not your fonts, it's your system locale. run locale to get your current locale configuration.
You can use something like LC_TIME=fr_FR ls -l to get France's format in date column as an example if it's available to use on your system.
You can also use locale -a to get a list of available locales. edit /etc/locale.gen file to enable your desired locales by removing # from any line you want, then run sudo locale-gen to generate them.
After all run:
sudo localectl set-locale LANG=en_US.utf8
to set English locale as your default or change en_US.utf8 with your desired locale.