Translate alert messages?

Can someone tell me, where i can translate the alert messages.

I’m using da_DK language, but the alerts is in english. I can provide danish translations if someone would like that. But i’m also interested in knowing where to translate them my self. As i would like some custom messages to be shown, instead.

Thank you ??

https://www.ads-software.com/plugins/redi-restaurant-reservation/