Hello Euromat Ελλάς Α.Ε,
It is definitely a possibility to add a page with your translated version of the product guide but you cannot replace the current one. If you head to our SDK link, https://geotab.github.io/sdk/software/guides/developing-addins/ you will see that you can add Pages into your MyGeotab Database in the form of Add-ins. This would be a work around for your customers if you'd like to just add a translated guide. You may also submit a Feature Request (https://www.geotab.com/blog/submitting-feature-requests/) as a reseller for Geotab to support the Greek language so the database as a whole can be in Greek.