What a terrible film; all the dialogue is over-dubbed, badly.
Robert Wise's 1975 version was bad, but this is worse; the VFX are obviously better, but the script, plot and dialogue here are just rock-bottom awful.
It's clear almost from the beginning that most of the dialogue is over-dubbed, even though the actors' lip-movements match the words. The American/English-speaking actors sound better and more natural than the German actors. What I think happened here, and this is just a guess, is that the film was shot in both German and English, with alternate takes of each scene in each language; the German actors and actresses spoke their lines in English for the English takes, but either their accents were too thick or they didn't actually speak English so they were just uttering the words phonetically without understanding them (as an English-speaking American might read aloud words written in a foreign language that he does not speak or understand). Hence the lines were later over-dubbed by voice actors who spoke better English, although the result is still pretty awful. Again, that's just a guess, but the dialogue is so obviously over-dubbed and sounds so bad that I can't think of any other reason for it.