A small update: I found out that the API from coinmarketcap via northpole.ro is stuck at July 25th at 13:00.
At https://github.com/mess110/coinmarketcap.northpole.ro/issues/23 other people have issues with it as well. First of all I am happy that I can use that API via them and I hope that t can be fixed soon. This so I can see where I am today with my challenge :).
Thanks for your time!