I've never used this, or investigated DeepL, and so haven't seen a pre-built solution, but looks like they post the details of the API pretty accessible.
That macro just constructs the text into a string to parse to the API.
Using this: https://developers.deepl.com/docs/api-reference/translate
You are probably looking for this: https://developers.deepl.com/docs/api-reference/document
Otherwise, you can make your file into one text field (with delimiter) and pass that to the translate API
