Hello Dustin,
I think you must keep this in mind - both in English and Korean, the subject is ONLY one.
Those particles - 은/는/이/가 - are subject particles, which means you need to use ONLY one of them for each sentence.
(although we call "은/는" the "Topic Marking Particles", they are used for the subject).
For example, you wrote,
Dustin drinks green tea.
다스틴은 녹차가 마시어요.
Do you see the problem?
(Good try, Dustin! but, now do you see why I mentioned the above)
더스틴 "은" and 녹차 "가"... you used two subject particles - 은 and 가, which means you have two subjects.
Many English sentences and Korean sentences are S + O + V sentence structure. (S=Subject, O=Object, V=Verb) - NOT be-verb but regular verb.
(subject) Dustin (object) green tea (verb) drinks. = Dustin drinks green tea.
YOU NEED PARTICLES AFTER SUBJECT (은/는/이/가) AND OBJECT (을/를).
therefore, 더스틴 "은" + 녹차 "를" + 마셔요. or 더스틴 "이" + 녹차 "를" + 마셔요.
더스틴은 녹차를 마셔요 or 더스틴이 녹차를 마셔요. This is a sentence.
Now compare it with what you wrote, 더스틴은 녹차가 마셔요, which means "Dustin drinks" and "green tea drinks" too.
Next, you wrote,
I'm eating bibimbab.
저는 비빔밥이 먹어요.
again, do you see what's something wrong?
how many subjects in this sentence? it has "TWO" subjects - 저는 and 비빔밥이.
This is also S + O + V sentence structure.
(subject) I + (object) Bibimbab + (verb) am eating = I am eating Bibimbab.
YOU NEED PARTICLES AFTER SUBJECT (은/는/이/가) AND OBJECT (을/를).
저 "는" + 비빔밥 "을" + 먹습니다. or 제 "가" + 비빔밥 "을" + 먹습니다.
Therefore, 저는 비빔밥을 먹습니다 or 제가 비빔밥을 먹습니다. This is a sentence.
Now compare it with what you wrote, 저는 비빔밥이 먹습니다, which means "I eat" and "Bibimbab also eats".
Last, you wrote,
The kimchi is over there.
저기는 김치가 있읍니다.
Dustin, "over there" can NOT be a subject.
The subject is Kimchi, right?
(subject) "Kimchi" 김치 "가" + (adverb) 저기에 (over there) + (verb) 있습니다 "there is"
김치가 저기에 있습니다.
Here is my tips for you.
If you see "regular verbs" such as "to eat, to see, to do, to watch..." then normally the sentence is S + O + V.
Therefore, use one 'subject particles' (choose one of 은/는/이/가) and use one of 'object particles' (을/를).
If you see "be-verb" such as "is, am, are" then, all you need is ONLY one subject particles (choose one of 은/는/이/가).
Dustin, forget about what you already know about Korean.
I think... somebody already taught you Korean without teaching any basics.
Think like this - if you want to be good at playing golf, you have to spend a lot of time on the basic swing.
If you want to be good at playing tennis, the same rule applies.
How about swimming, baseball, soccer, any other sports? Without basics, you wouldn't improve yourself.
The same rule applies in learning a new language. Go back to the basics and start over learning basics.
cheers,
Tim