It is best to listen to Korean to understand how it sounds. Trying to equate it to English letters is very confusing. In English, one letter can make many different sounds. Listen to Korean as often as you can. Practice. https://www.youtube.com/watch?v=022XIdivHVU&list=PL7UGhRCG9Ki4mxDX4sNJ9U2py1Lg1TDkN ㅅ before ㅑ,ㅒ,ㅕ,ㅖ,ㅛ,ㅠ,ㅣ sounds like "shhhh" Otherwise it sounds like a very soft, gentle "ssssss" (like a snake, but don't hiss) The "zzzzz" sound (buzzing like a bee) does not exist in Korean. ㅉ is a hard sound that sounds a bit like "zzzhhh".

wow~how did u learn it? I learn it just about twenty days(๑• . •๑)

You're welcome! I have been learning Korean for six months now (officially - I had studied off an on for a while in the past). How long have you been learning Korean?