Problem with changing the names of the navigation buttons

[PetervanBreda]

I hope that somebody can help me. I have been spending hours on finding the way to change the text that is written on the navigation buttons: it concerns the texts Popular products, Latest Products and Best Sellers. A little bit more down on the page there is a button with the text Onsale. The texts must be changed into the Czech language. I ordered a module called Luxury. Many things were translated in Czech language. Or I was able to find it. But how to change these texts (Popular products, etc) I can not find.

I have been looking for hours. In the the themes modules (starting with ps_), in the database. Everywhere.

Can somebody tell me where to change it?

Thank you in advance.