Wie können die Tiere bei König der Löwen/Mufasa reden und überhaupt so gefilmt werden?

The animals are acting animals that were specially cast for the films. You already have film experiences in other films, e.g. in Star Wars (including the Cantina Bar). Therefore they play their roles as natural and not as ordinary pets or zoo animals.
Of course, they do not speak the language in which the film is shown. They are synchronized like human actors. Her native languages are predominantly African and Indian, as well as French.