I change the language but translations not working

- make sure that the PHP extension gettext is installed into your server
- double check if your server have the correct language locale installed, for example de_DE for Germany. If you have ssh access to your server run the command locale -a to check it.
- if the language is not listed in the above output, run these commands to install it: locale-gen de_DE and locale-gen de_DE.UTF-8
- restart the web server