All the "O" class vowels are pronounced with an "oh" sound. "O" class vowels are usually transliterated with the letter "o". The vav of holam vav is a matres lectionis—it is not a consonant but acts as a vowel. This is an ancient tradition known from exilic times before the Masorites added nikkud to the Hebrew text.
The hataf kamats only occurs with the guttural letters [א ה ח ע].
The kamats hatuf is sometimes called kamats katan (small). It is important to note the visual similarity to the "a" type vowel kamats (sometimes called kamats gadol, meaning "big"]. The two vowels have very different sounds.
Practice. ...Putting things together.
Listen to and practice saying these consonant-vowel combinations. Each combination, whether open or closed, represents a syllable.
