Translation:Eating cake every day is not good for you.
Your answer would certainly be understood as having the same meaning as the one provided. And of course these two versions are very close, essentially differing only in your use of the infinitive where the "correct" one uses the gerund. As a native (US) English speaker, I would say that "Eating ..." sounds more common and natural, and that, when a verb forms the subject of a sentence (as here), the gerund is more commonly used; e.g., "Driving is easy," "Being sick is no fun," or "Learning a foreign language takes patience."
Do you mean the infinitive? The infinitive is the form of a verb that we typically find in dictionaries: sevmek, almak, etmek. In English, the infinitive is often written with "to" in front (e.g., "to be," "to go"), though generally not in dictionary listings. You can think of the infinitive as the "standard," "neutral," or "basic" form of a verb. It may be contrasted with conjugated forms that reflect particular persons (I, you, s/he), number (singular, plural), tense, or mood. As for being confused, I think that some struggle and confusion are natural parts of the learning process, so don't despair!