When you update GeneratePress, you will need to re-add your language files to the languages folder.
To prevent having to do this, you can:
a) Send me the files to include in GeneratePress by default – 188.8.131.52 has already been uploaded, so you would have to re-add them once, but they would be added by default in 184.108.40.206.
b) Add your language files to your child theme: https://codex.wordpress.org/Function_Reference/load_child_theme_textdomain#Example
Let me know if you need more info 🙂