The multi-sound characters are common in usage. For example 长 can be cháng meaning "long" or zhǎng meaning "to grow". 行 is xíng "to walk" or háng with no real single coherent meaning, appearing in compounds like 银行 yínháng "bank" and 行业 hángyè "profession". All of these are very common usages. In context they are essentially never ambiguous, but if you are going through character-by-character it's not going to make sense.