Rémy (débutant sans micro)

[lament sky]

Please be patient

Our volunteers look into many questions every day; sometimes it takes them a little while to answer.

Pro tip: you can rename the thread title with `.tr <thread name>`

Make it descriptive, including relevant context, but also to the point. This way you improve your chances of getting a more relevant and specific answer.

[drowsy ocean]

(1) « connaissance » is the COD plus the object before the verb is indirect so that's a COI, and COIs don't do agreement
(2) The expression takes an indirect object under de : « faire connaissance de qqn »

Same reason as to why you have « C'est la clé dont j'ai besoin » instead of « *C'est la clé que j'ai besoin » because the expression takes an indirect object under « de », « avoir besoin de qqch/qqn »

[north dome]

That makes sense and that's a really good example thanks Bertiebear!

[drowsy ocean]

« que » only works to replace direct objects

indirect objects have a specific structure :
« préposition + lequel/laquelle/lesquels/lesquelles »

lequel agrees with the object it is replacing

For example :
« La république pour laquelle je me bats est grande. »
« Les droits pour lesquels je me bats sont grands. »

The first has « laquelle » agreeing with « la république », while the second has « lesquels » agreeing with « les droits »

The exception here is « de + objet » where instead of that preposition + lequel structure you have just « dont ». Of course, French being French, there’s an exception; it doesn’t work with prepositional phrases