German has two distinctly different sounds that are represented by the letter combination ch.
The so-called back ch is pronounced in the back of the mouth. It is usually preceded by a, o, u, or au. Although this sound does not exist for most English speakers, it does occur in Scottish English in words like Loch (as in Loch Ness).
The front ch, produced in the front of the mouth, follows all other vowels and diphthongs and also occurs at the beginning of a word. The front ch is similar to the English h in huge. Another way to approach the sound is to say the intial y-sound as in yes in a prolonged manner (“yyyyyyyy”) and then drop the voicing and force air out through the mouth opening.
How ch is pronounced is determined by its phonetic environment, i.e., by the vowel sounds that precede it, so if your mouth is positioned correctly for articulating those vowels, then your mouth will already be where it needs to be to correctly pronounce the ch-sound.
Note that the chs combination produces a different sound much like the English combination ks.
Listen to these words and repeat to become familiar with the distinction between these two sounds:
Practice recognizing and pronouncing front and back ch
Here are some words with front and back ch-sounds. Read each word aloud. Then play the audio to verify your pronunication.