The text is part of the language files, see here:
translate.limesurvey.org/projects/limesu...lation_id%5D=1797262
So you would have to change this in the translation file, which I don't recommend, because your adaptions can be overwritten with any update.
But just adapt your survey template and put your own link and text into the template, then you can adapt this to your liking.
You could also try to suggest to change the official translation of "privacy policy" from "Datenschutzerklärung" zu "Hinweise zum Datenschutz", but to be honest I find the current translation better/more accurate compared to the English basis. So I doubt this suggestion would make it through. I think it is rather a persona preference (should be clear to anyone what to expect with both wordings).
Regarding your second question: No idea. But similar, create your own file you will link to in the template, that way you will have more freedom in your choices.