Actually, Google Translate is not much worse then DeepL - and it's integrated in the translation feature of SoSci Survey (i.e., the table view that displays the translations side-by-side).
> deepL only accepts pdf, word and / or ppt
You can give it a try and put a table in a Word file to feed it to DeepL. However, if the free version of DeepL does not like to translate tables, than you won't be able to use it to translate tables.
> I could go over each question manually (using DeepL) and input it into the existing excel file and then save everything as a csv and try to upload it.
Seems like the "online table" in the translation assistant would be a bit easier than opening each question.