Currently, it is not possible to translate Gravity Forms directly from our plugin. Gravity Forms however already provides its own translations as well as the ability to modify the existing translations by way of making changes in the PO file.
If you need custom translations, we are able to translate the PO file if you provide it to us. This will need to be sent to us outside of the plugin.
For more information on translating Gravity Forms, please visit: https://www.gravityhelp.com/downloads/translations/