The "ch" in English is usually pronounced as the first sound in "china" (the fruit also known as "naranja"). It is pronounced by puckering your lips slightly and placing the tip of the tongue on the upper tooth ridge. There is a small explosion of air as the tongue moves downward and away from the tooth ridge.
A problem could arise when the letters "ch" are pronounced as "k" as in the Spanish word "coco". This is the case when pronouncing the word "character" (ká-rak-ter).
I hope this helps.
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