Single Page Menu

Hi there,
I followed your documentation how to create a Single Page Menu and I think I did everything like is wrote there, but my menu is not working. Instead of scrolling down to the “#section_name”, the page opens again. In addition, menu is now duplicated in the top bar. Another strange thing is when I add / at the finish of the url (https://www.sicilyparagliding.it/info/#section_prezzi/) whole page breaks.
Please help me, I have no idea how to fix it.