I suggest you use the latest version of sellacious, which has many more features like SMS, chat between sellers/buyers, updated Delivery/Pickup Extension, Hyperlocal, etc. You can check the demo here. https://demo.sellacious.com/squick
As for the language key, go to language/en-GB/en-GB.tpl_squick.ini
. Check the folder of the language you are using on your site.
I hope this helps.
Thank You & Stay Safe