There are at least three ways to pronounce the letters <ch> in English:
/ch/ as in cheese
/sh/ as in ship
/k/ as in kid.
See and listen to a list of examples here ch.
English and her history
In Old English the sounds (k) and (ch) were both represented by the letter c. Later, under the influence of French spelling, Middle English scribes inserted an h after c to indicate the (ch) sound at the beginning of words, as in child. (The sequence tch became the usual way to represent this sound following short vowels, as in catch.) In English words of Greek origin the digraph ch represents a transliteration of Greek X (chi), and so is usually pronounced (k), as in chorus, architect. And in English words borrowed from French, ch is often pronounced (sh), as in charlatan, cachet.
Source § 45. Ch. 7. Pronunciation Challenges. The American Heritage Book of English Usage. 1996