The solutions can only be downloaded via the coordinating teacher's user account - if you are the coordinating teacher at your school and you don't have access anymore, you can use the magic link from the confirmation e-mail you received when registering for the contest.
Click on the big green button "Find out the results of the 2020 contest here! Then go to your 2020 participation and select "Answers". You will then be taken to a new, separate page where you will see the correct answers per question and level. You can also download the solutions as a PDF.