Here's what I tried:
But I need help to find out how to get latitude and longitude of the user's destination... Could you help?
So basically you need to find lat and lng from the adress given? If so you need to geocode the address. Read OpenRouteService-Geocode. Use web component and dictionary blocks to get coordinates
How is the destination chosen?
From touching the map?
From a list of place names?
Pre-entered list?
You might get specific advice on your own by answering ABG's questions.
I guess all you might need to do is make this change
If you don't want to do that, perhaps these three tutorials will help: