Sounds very promising, Stijn!
The biggest risk is to quite all together. Always better to do a little something than nothing at all. One tends to crave constant improvements. Donīt fall in that pit. Many times you will hate it, quit as you feel too tired or lost your enthusiasm. A lot of times the reason spells over training. Accepting that building a decent physic takes a long time is the key. Some days a couple of kilometers is good enough. Some periods a couple of weeks off is necessary.
At first I thought you meant running - 15 km in 30 minutes!?!
You mean bicycle, donīt you ??