Red, from Syria, asks, "How can I become better in knowing the differences between stressed and unstressed syllables beside practice ? Is there a secret I could use to seperate between stressed and unstressed syllables ? Thank you"

Hi Red, this is a tricky question, because the answer is different for every language. I'm going to hope that, since you're not from an English-speaking country, and you're writing to someone who answers questions in English, you want an answer about the English language. English is a very unpredictable language. Some languages, like Spanish, have very hard-and-fast rules for defining which syllable receives the stress (accent). English...not so much. But there are still some guidelines that will help you out. I'll cover a few here to get you started.

1. In general, we consider every English word to have one accented syllable. However, if it's a lengthy word, we might have syllables with a "secondary" stress. For example, we might say that the word "dodecahedron" has its stress on the syllable "dec" and a secondary stress on "hed." Notice that the pattern of stressed and unstressed syllables is an alternating pattern: do-DEC-a-HED-ron. This alternating pattern is quite common.
2. If a word has either a prefix or a suffix, it's unlikely that the accent falls on the either the prefix or suffix. For example, in the word "unlikely," "un" is a prefix and "ly" is a suffix, and both are unaccented. This leaves us with the inevitable conclusion that "like" is the accented syllable. Lest you think that's a guaranteed rule, just scan through this paragraph, and you'll find a counter-example: "prefix" is pronounced "PRE-fix," not "pre-FIX."
3. When in doubt, find the first syllable that isn't a prefix, and give that one the accent. That's also not a hard-and-fast rule, for sure, but it'll be correct more often than it's not. Consider the word "unpredictable" in the first paragraph of my response. "Un" and "pre" are prefixes, so we put the stress on "dict": "un-pre-DICT-able."
4. Some words have different pronunciations depending on the way the word is used. For example, the word "refund" can mean "an amount of money returned" or "to return some money." The first one (a noun) is "RE-fund" and the second (a verb) is "re-FUND." When faced with this sort of word, the safest guess is to assume that the noun has the first syllable stressed (even if, as is the case here, the first syllable is a prefix), and the verb has the next syllable stressed.
5. There are a few other rules you'll figure out as you go along, and the more you hear English spoken, the more you'll intuitively grasp them. For example, if you run into a word that ends with "ation," it's very likely that the penultimate syllable will have either the stress or the secondary stress, which will help you work out how to pronounce the word. Examples: pro-NUN-ci-A-tion, in-TER-pret-A-tion, etc.

Hopefully this will be helpful to you in learning better pronunciation. Of course, there is no substitute for spending time talking with native speakers and picking up their speech patterns! Thanks for your question, Red.