So I can think of a few options, one is just cleaning up the code you shared a little to reduce some code
let language = wixWindow.multilingual.currentLanguage;
let header = "Prisperiode"
if( language === "en"){
header = "Price Period"
}
else if (language ==="de"){
header = "Preise im Zeitraum"
}
$w('#table1').rows[0]["prisperiode"] = header
The other is perhaps to maintain different collections by language and just swap out the data reference for the table in code?
There may be other ideas around but that’s what came to mind first. Also, I would reach out to customer care and submit a feature request for this to be an OOTB functionality for multilingual so you wouldn’t have to do the manual translation in the future ideally