It is well-known that the spelling of a word in English doesn't always match the pronunciation of that word. This can cause frustration for learners but there are ways to try to make sense of this aspect of English.
Try to focus on the most common words which have silent letters; words that you will use more often than others. Also, listen closely to how native speakers say these words in natural conversation. For example, when shop assistants ask you if you want a receipt, they will not pronounce the "p". Being more aware of this will help you to pronounce such words properly.
See the link at the bottom of the page for a list of silent letters.