Another problem with learning these pronunciations is the fact that a massive sound change happened to the English vowel system quite recently in our history, which creates a huge difference between the way the Anglo-Saxons spelled vowel sounds and the way we do. Old English vowels are more like continental European vowels than they are like Modern English vowels. From this point of view, it is easier to learn Old English if your first language is French or Italian than if your first language is English. We don't have one of these in Modern English, so if you don't know other languages you may not have encountered it. Short u is pronounced like the vowel in put or foot .
Short o is like the o in pot .
A dipthong is a glide from one vowel sound to another pronounced as a single syllable.