I don't understand the purpose of the first paragraph, and I don't think that you need it there. It's generic and you should generally avoid saying things like "we should do this this" or "we have tendency to think this way". You only have 250 words, be personal!
Since I was little, I showed a great interest into helping people, especially children
That'd be a much better start of your essay.
Besides children, learning and mathematics are my passion.
there's absolutely no transition here. You put 1 sentence out there about helping people, and move on to math and LEARNING? never EVER put learning as a passion, it's like saying "I like bleh..."
now, you need to develop on the idea of helping people. Don't start talking about something, then immediately going off about somethign else. I suggest that you spend at least 1 paragraph on a SPECIFIC and PERSONAL example about helping people/kids.
Before high school, I heard a lot of students saying negative things about biology and especially chemistry.
where does that come from? You just mentioned math/bleh, now it's bio and chem? come on, have some focus!
Your third paragraph is definitely out of place, it should've been right after you said: I like to help people. It's still very broad. You talk about how you are
strong, disciplined, determined, and willing to take any challenge and opportunity
, yet I can say the same thing and it wouldn't matter at ALL. You can't just say good things about yourself without ANY sort of support. It's like writing a research paper solely based on hypothesis and conjecture, without experimentation/actual data to back it up.
I'd suggest you structuring your essay this way:
find your focus, do you want to talk about kids? If so, try to tie your major to it. Math/science? works 2. CHOOSE 1 out of these 2. you've only got 250 words, no time to go back and forth.
1st paragraph: come up with an interesting intro. the beginning of a story for example. college essays should be personal stories that respond to the prompt, not scattered theses all over the place.
2nd paragraph: using that story or short anecdote, link your interest to that. For instance, you could talk about the emotions you felt on the podium after winning a bio/chem contest in the first paragraph, and in depth about how you've come to like the subject, and what part of it you like (don't get technical here). you need to keep the reader interested by telling a story, not showing off the bit of knowledge you know about these subjects, or worse, mention them in a general way that could be done by ANYONE. remember, you are 1 out of 1000, stand out!
3rd paragraph: conclude. If you don't have space left, don't. a conclusion is unnecessary, but if you feel like it, do it.
overall, if you wish to have an essay that actually will help you, rewrite it in a much more personal way. The reader wants to know about you, and it's not through mentioning your interests, which are very typical of Asians anyway, that'll pull you through.