i wrote this as i go through your essay, so my opinion will change from time to time...so please read the entire thing before countering any impression i have on your essay
So your self given prompt is
We know that a coin has two sides. But what about a medal?
? if so, do you really answer it? do you ever talk about whether a medal has 2 sides, and what they are?
in any case, simply focusing on the quality of the essay (not considering grammatical mistakes), your essay seems convoluted. assuming that you do answer the prompt (i suggest you coming up with a prompt that "fits" better your essay), it lacks a clear thesis.
your intro states that you wanted that medal, and your 1st body declares how you realized that
it did not shine
. at that point, it's expected that you keep running with the idea that this medal didn't provide you with the pleasure you supposed because of the sacrifices and such
however, your third paragraph talks about how the medal was actually worth something since it was the zenith of your efforts.
ok, upon reading your conclusion, i think i get your point: the medal has its downsides, and its upsides. however, if that is your thesis, then you need not to say in the second paragraph that the medal meant nothing, because if it did, then there wouldn't be any point to your essay, but whether the medal was worth all the trouble.
i'd take out the michael phelps part. it distracts the reader from your main point.
overall, i think that you really do need more focus. i'd suggest:
2nd paragraph focus on your sacrifices (was the medal worth it?)
3rd paragraph focus on the upsides
conclusion, the medal told the story of your life, and was definitely worth it.
(that's why i'd change the prompt...you don't want a prompt that requires qualification, like qualifying both sides of the medal, but whether the medal impacted you positively)
when you write about the downsides and upsides, talk in specific. Don't try to go all over the place and list all the things you could think of. instead talk about 1 or 2 or 3 specific events that were really significant to you that illustrate your sacrifice or your gain; also, what confuses me is when you try to explain the upsides with the downsides, like that despite the fact the you lost friends (downside), you made new ones. i'd try coming up with more significant examples, specific to the IMO competitions. after all, you could lose friends because of anything, not necessarily math competitions.