Hi Mourad,
Thanks for getting in touch!
Sorry for the missing files here. If Arabic is missing, then that’s defiintely an oversight. You can check the previous version of The Events Calendar (direct link to ZIP) to see if the files existed there and use those as a foundation for updating them to the current version of the plugin (3.10.1).
We do rely on the community for translations and would definitely be happy to accept contributions from you or anyone else who is interested. In fact, we have a site dedicated just for those types of submissions and I’d love to see those come in. You’re welcome to submit the first round of Arabic translations to me here in this thread and I’d be happy to set that up on the site to allow for more contributions. 🙂
Cheers!
Geoff