Syllables that are stressed can present complications when trying to learn a language. Not all languages use stress like English does. In French there is no stress for individual words, although there is intonation (the rhythm and flow of speech) when you are asking a question, which is a different topic altogether.
The rules for assigning stress in English are quite complex and usually has to be memorized. Words that appear similar can have completely different stress rules. This can confuse people that are just learning English language.
For example: Say photograph then pronounce photographer
Notice that these 2 words are very similar and will even appear in the dictionary as one entry. For Photograph, stress the 1st syllable. For photographer, the second syllable is stressed. Even if you stress the wrong syllable, most English speakers will still know what you mean.
I often get asked....."Is there an easy rule for determining which syllables are stressed in English."? My answer is no. Some languages have a predictable stress rules. Keep this in mind, when one learns new English words, the stress patterns and the word must be memorized, including the definition.