To be more precise: "je" is pronounced /jə/ (like the e in the German "bitte") while "jij" is pronounced with a diphthong /jɛi/ which sounds a bit (albeit not exactly) like "yay". The English equivalent would be "ge" or "ye" (pronounced with an /e/, not the /i/ that you would commonly pronounce it nowadays) which we got rid of when it merged with its objective declension "you".
- je/jij, ze/zij, we/wij: https://www.duolingo.com/comment/3734337
- de/het: https://www.duolingo.com/comment/3732938
- verb conjugation (present simple): https://www.duolingo.com/comment/3762671
Overview of topics: https://www.duolingo.com/comment/3732817
PS. There is also information on each skill page, at least on the website. E.g. verb conjugation at the bottom of: https://www.duolingo.com/skill/dn/Basics-1
Suppose that would be close enough, have a further look here: http://www.heardutchhere.net/DutchPronunciation.html#IJ