Here are my original impressions:
you use two subjects in the first sentence so is should be "are not everything".
the paragraph is pretty choppy. You say that the author makes a point about bullfighting and that is imagery but you never directly state the purpose but rather go about it in a half-arsed way. Consider the following revision: "In the novel, Hemingway's purpose is to examine the role of strength and masculinity not only in animal nature but also in human nature. He accomplishes this by an effective use of imagery and metaphor with bulls and bullfighting. His statement is that bulls are (fill in here) and bullfighting is (fill in here). His purpose is further progressed by (insert stuff here if you want). (now comes time for the thesis). However, as an individual meanders through the twists of his or her existense, a limit becomes apparent in adhering to the values of strength and masculinity and at one point, they must be replaced with (insert stuff here).
Here's what's wrong with your writing:
It's incoherent and sloppy. Your thought process may be great but the writing is not very logical or flowing. You need to ensure that your ideas are presented and that you have ample, clear supports. As for your thesis, I liked that you used a clause and restated your original assumptions but it is very lacking. The thesis, as was stated, merely wished to expound on the idea that masculinity is lacking. In the thesis, you should state WHAT it's lacking and also offer an alternative. An essay is very much like an argument. If I were to read the old thesis, I could say "wow, great, another freaking person saying I need to have feelings". And I would expect the writer to tell me that I need to have feelings. But the way the thesis was stated, there was no "why" and there was no proposed alternative. Try it my way and organize the essay in the format suggested. In case you missed it, the format is to tell them about the book (what Hemingway said and how he did it), analyze the book and state what he was trying to say, and lastly, state the solution either proposed by you or the author or make an allusion to another literary work.
That should make for a good essay.
Good luck 🙂