For the second onboarding challenge prompt I tried filtering on the explore page, on android and pc, however the filtering request gets a gateway timeout.

Request url ist the following:
https://app.thestorygraph.com/filter?mood_adventurous=true&mood_emotional=true&mood_reflective=true&moods_and_or=and&pace_medium=true&type_fiction=true&genre_include=include_any&genres_exclude%5B%5D=12&number_of_pages_less_300=true&from_original_publication_year=2010&to_original_publication_year=2020&search_term=&last_sort=Last%20updated&commit=Filter

If I change all the selected moods to any it works, although it takes about 49s (granted my wifi currently is rather slow, but on my phone without wifi its not thaat much faster).
I hope this information helps! :)