It is no longer possible to explain what is wrong with some items on the programme - we are not just dealing with errors in English sentences. If Duo wants users to help improving the programme, then it should be possible to make appropriate comments/ suggestions.
In work3 you show a picture of a carpet and states that carpeta means carpet. Later it reoccurs as plural carpetas. I translated it as carpets. It was marked as wrong. The meaning was given as folders. I checked it in a Spanish dictionary the word carpeta is defined as folder/file. PLEASE CHECK BEFORE POSTING WORDS.