Crossword challenge!

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Across
  1. 3. see, saw, ???
  2. 4. <-> right
  3. 8. Big Ben is a big ???
  4. 9. Feuerwehrmann/ -frau
  5. 13. It means that something is difficult to take up or carry.
  6. 15. It's an interesting or famous thing to see in a city.
  7. 17. think, ???, ???
  8. 18. überrascht
  9. 20. It's a place where criminals must go.
  10. 21. schon
  11. 22. It's a person who writes plays or books.
  12. 24. geschehen, passieren
  13. 25. sing, sang, ???
  14. 27. It's the money you get back when you pay something.
  15. 28. do, did, ???
  16. 29. It’s a place where buses or trains stop.
  17. 33. It’s a person who owns some land or buildings.
  18. 34. forget, forgot, ???
  19. 35. You can walk across it over water.
  20. 36. Big Ben's real name is Elizabeth ???
  21. 37. eat, ate, ???
Down
  1. 1. vorsichtig, sorgfältig
  2. 2. bald
  3. 5. <-> everybody
  4. 6. <-> expensive
  5. 7. fangen
  6. 10. <-> take down
  7. 11. <-> shout
  8. 12. Dach
  9. 14. Schauspieler
  10. 16. write, wrote, ???
  11. 17. A circus is usually in a ???
  12. 19. take, took, ???
  13. 23. Tochter
  14. 26. go, went, ???
  15. 30. Wortschatz
  16. 31. It's a place where you can buy things or food at stalls.
  17. 32. <-> started
  18. 34. kostenlos