Of these English and French are often the most difficult because of the many diphthongs. Italian and Latin are much easier as the vowels tend to be more pure. German has more unusual vowels and is a more guttural language, although the singing German is not quite like the spoken German. The point of this is that while languages are different one is always concerned about singing with an open throat with open vowels. One of the peculiarities we have with English and with French are diphthongs and in some cases trip thongs.
Diphthongs are more than one vowel together.
For example, day is deh-ee. In the case of diphthongs the first vowel is sung or stressed and the second is diminished or thrown away. With trip thongs the first and third are the sung vowels usually. As a singer we want to concentrate on the sung vowel. The progression of elongation is from left to right.