I want to say "I usually eat bread" in Korea, so I translate that sentence like this: "저는 자주 빵을 막는다". I wonder if the tense of my translated sentence is "present simple" and if that translated sentence has the same meaning with the English sentence
The tense is correct. 먹는다 (not 막는다) is in the present simple tense.
You can make these improvements to make it more accurate and natural.
- 자주 is more like "frequently" or "often". 보통 is the common word for "usually".
- -는다 is a sentence ending form used more in writing. In adult conversation, 먹어요 is better.
- 나는 is what's called a plain form without a polite feel. Saying 저는 is more polite.
So you can say: 저는 보통 빵을 먹어요, where -어요 is a polite sounding sentence ending in the present simple tense.
In addition to Tony's answer, you normally can't say "저는... 먹는다": "저" is a polite way to say "I," so it must pair with a polite verb ending such as "먹어요" or "먹습니다." Similarly, "나" normally pairs with 먹어/먹는다/etc.
If you're talking to a friend, you could say "나는 보통 빵을 먹어." If you're writing a diary or a novel, you may use a more formal expression: "나는 보통 빵을 먹는다."
- Sometimes people do say "나는 보통 빵을 먹어요" (which would be semi-polite) although some people consider that bad style (because of mismatched politeness level).