Did you copy and paste the German text into a new Pages document and if needed separate the paragraphs with a return, then select the German text and right-click to chose Translate…? When I did this with five paragraphs of German from Lingua, it resulted in replaced English text with four simple errors to correct. I am using Grammarly for Mac Desktop (without a Grammarly account). Otherwise, each red line can be right-clicked and either ignored, corrected, or added to the dictionary — a royal PITA if there are many.
An expression of "not far to the BrandenBurg Gate" was suggested to repace "to" with "from." Another was a case of "restaurants, shops and hotels." was suggesting a comma after "shops."
Another "sights are really worthwhile" was suggested as "sights are worthwhile". and finally "our hotel also offers its own city tours" changed to "our hotel also offers its city tours."
When I switched off Grammarly in Pages for an hour and told Pages to check the document, it only flagged the word "Große" as not found in the dictionary.
Original German text