I'd like something like that for French. I've extreme difficulty to differentiate between "deux", "de" and "des" among other very similar phonemes that are so common in the French language.
They have lots of videos that go into the different pronunciations of specific phonemes, and will for example teach you when to use the open or closed variation for a word.
As for OP, the site just gives a score? How does one know how to improve with that? I was expecting something like "you pronounced this vowel like this when it should be like that"
French here, a few tips:
«deux» and «de» are pronounced the same (almost everywhere at least). The only thing that change is the «liaison»: if you have «deux» in from of a word that starts with a vowel, then you'll need to add a “Z” sound in between: ex. «deux animaux» is being pronounced as if it was spelled «deux Zanimaux».
«des» sounds different, it pronounces like «dé» with an «é» sound like in «thé» or «café», and since it finishes with a “s”, you have a «liaison» as well: «des animaux» => «des Zanimaux».
I feel like anyone with children and the opportunity to do so should try to expose them to as broad a set of phonemes as possible from an early age.