To be honest, Sergio, I think Mr Mic’s advice was pretty darn good and I can’t think of anything better. Maybe you could try singing the word and counting the beats. (seriously)
When I count syllables, I do it by saying the word slowly and clearly and counting on my fingers as each syllable comes out of my mouth. This naturally works best for words that have 10 syllables or less (Oops! I think I should have said fewer…;))
Even native speakers sometimes come across unknown words while reading that they don’t know how to pronounce. That’s one of the difficulties of English. It’s not always obvious how to pronounce words.
Maybe if you posted a few of the words where you think it’s difficult to count the number of syllables, someone might have another idea for you.