Well to be honest I don't know why sometimes some links are missing. Most of the time it's just one of them. Maria is marked as sister of John, but he isn't marked as her brother. And therefore you don't see anything wrong in your data.
I don't know who made the french translation and my french isn't good enough to say something about it's quality. But I think it's more a problem about the strange thing we can do here than it is a literally translation.
"Correction des caractères" is used to correct character (at least ä, ö, ü, ß are tested) which may be imported from a gedcom (or copied from a website through the clipboard) and are coded with the wrong character set.
"Eliminer les espaces" is used to delete spaces which were entered accidentally by the user. E.g.: " Marcus" in the name field or "Marcus " will be changed to "Marcus".
With
"Parents / Fratrie / Partenaires / Enfants" the corresponding field in the edit-dialoge are meant. You can select here, if you want to see the all first names of a person in these field or just the nickname by which a person is called.
I you're unsure about some tweaks and possibillities just ask here or save a test-file of your family (TEST.ahn) and play a little with all the functions that Ahnenblatt offers.
Marcus