Saying "He eats bread" or "He is eating bread" is correct. I've never tried "He eats of the bread." When you translate something into another language, then translate it back, there's a possibility the sentence has different grammar then the original sentence you wrote. (Example: English to Japanese to English again.)
*in french the two sentences are the same. and can be translated as "le garcon mange du pain" .
*also you can translate "The boy is eating bread" as "le garcon est en train de manger du pain" .
*note : we use the expression "etre en train de " to express present continous tense.
English has two present tenses: simple ("I write") and continuous ("I am writing"), but French has no specialized continuous verb tenses. This means that "I write", "I am writing", and "I do write" can translate to j'écris (not je suis écris) and vice versa.
However, the idiomatic phrase « être en train de » is often used to indicate that someone is in the process of doing something.<pre>
Je suis en train de manger. — I am [in the process of] eating.</pre>
When translating, remember that English stative verbs have no continuous forms. For instance, « j'aime un garçon » cannot be translated as "I am loving a boy".
TL/DR: The phrase "I write" and "I am writing" are said the same way in French, namely, "J'écris." Context will determine which nuance is appropriate.