Convert a two-family house into two condominiums. What will be done there?

Hello,

can someone explain to me what exactly is done when the owner of a two-family house sells it to 2 parties?
The property must somehow be divided. Who owns which basement, how is the land around the house divided, etc.?
What steps are taken? Surely a notary is always involved, right?

Thank you for any information or links on the topic

Mandatory declaration of division by the notary - he advises on this (the apartments must also be separate = certificate of separateness). Normally, each owner then owns their apartment; for cellars/outdoor facilities etc., there will be special usage rights, as these are common property.