You most probably wrote 私は意欲的な人間だから、一生懸命勉強します。 ＝　わたしは　いよくてきな　にんげん　だから、　いっしょうけんめい　べんきょう　します。 [I put spaces for readability, but Japanese people do no write like this] = I am a motivated human being, so I'm going to study as hard as possible. ^This sentence is very unnatural mainly because にんげん translates to human not person, but also because Japanese people don't normally compliment themselves

Hello! I suppose, Because I'm an ambitious human, I'll spare no effort in studing.