Please go to https://translations.launchpad.net/linuxmint/latest/+pots/cinnamon if you want to translate Cinnamon in your language or improve existing translations.
Some languages are still missing sentences. So far some 15 languages are finished. But of course improvements for finished languages are also welcome.

You can also join a Linux Mint translation team if you wish: https://translations.launchpad.net/+groups/linux-mint