what's the difference between 걷 , 겆 , 겄 , 것 , 겉 ????
it says that 걷 , 겆 , 겄 , 것 , 겉 are all pronounced 'gat' how can I know which one is which, I'm confused.
They're only pronounced the same when standing alone or at the end of a word. If there's a vowel after them, you pronounce the 받침 letters. Like 겄어 is pronounced differently than 겉어 or 겆어.
But like any language, there is some spelling memorization required, but Korean is far more consistent in this regard than most other languages.
https://www.youtube.com/watch?v=EHe9IJcUXCw explanation of 받침 by a native Korean.
https://www.youtube.com/watch?v=hCewGEOaWeo 1 of 4 "sound change" videos by Billy.
Try to get away from Romanization as soon as you can if you want to truly learn the pronunciation. I don't know how you pronounce "gat", but it is really not representative of the Korean syllables you are showing. The "ㄱ" can resemble either a "g" or a "k", depending on position and surrounding letters, but it is not exactly like either one. The 어 vowel is rarely represented by an "a", except maybe the unstressed "a" in "another, but that is only a rough approximation. The Korean 어 is a more open-mouthed sound. If you havn't already done so, you might try one of the several excellent Youtube hangul courses taught by native Koreans. It would be an hour well spent.
https://www.youtube.com/watch?v=VmCiZfHq7xYt=25s (pronunciation practice)
This fellow has his own home page https://www.youtube.com/channel/UCYh6ilkmW_wXmSgqq-xdqUQ
and numerous Youtube postings. He is a very effective Korean teacher, as well as being entertaining with his art work and humor.
Well. they are all pronounced the same, that's one of the difficulties of Korean, as well as multiple other languages. You just have to remember the spelling of the words they're used in, and if you have a "type what you hear" exercise, you have to able to recall how to spell the word that you hear.