Translate image captions

I have to translate https://www.italianluxuryboat.com page. Everything is ok, but my homepage captions, are text on images, and they dont have option to be translated, how can i solve this problem, please someone help?

p.s. These text on homepage is: Big title text is image title, and little text is alt text on images. And every slide is image with its own title and alt. And plugin dont see these text as needed to be translate…

I hope you can understand what i’m saying…:D

https://www.ads-software.com/plugins/transposh-translation-filter-for-wordpress/