Ciao Riccardo,
Welcome to the world of sailing I hope you have a great time with your family.
Regrading the keel, as Nizam has said be sure you are measuring the right thing.
Re antifoul, if you are sailing the inland waterways of the Dutch canals you may find it best to check what other locals use for antifoul (and indeed for anodes) as it may differ in fresh or brackish water from salty sea water. If an Association member from the waterways does not reply it may be useful to see who is local to you (https://www.dufour.org.uk/members-boat-map/) and send a message direct or ask in a local chandlery.
The membership association for owners of Dufour Yachts