The problem with your text is not that it’s not sufficiently formal. The problem is that it’s difficult to understand what you’re writing. I have heard this thing before about students wanting to make their texts more formal. When I hear this it really annoys me. First of all a text should be comprehensible and written in a clear language. Don’t strive for formality, strive for clarity. The purpose of language is to make oneself understood. If your tutor doesn’t agree with that then I think you should find another tutor, because then he or she is in my opinion an incompetent fool.