If you choose to take the test again, then you should find out the exact policies that those colleges follow with accepting SAT scores. Some colleges will only consider the highest submitted score for each category, while others will consider all of the scores submitted.
If they only look at your highest score, than you might want to take the test again. If they look at all of your scores, then you need to account for the possibility that your writing and reading scores will drop the next time that you take it. In the second case, I don’t know if it is worth the risk.
Geometry is very prevalent on the SAT. Here is one pdf document that shows the sort of geometry that is common.
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As for the college essay, the most important thing to try and do is to make it unique and memorable.
I am going to assume that the topic of the essay is “Why do you want to attend this school?” Personally, I will try and stay away from the argument of “it will help me get a high-paying job.” I would instead opt for an answer along the lines of “helping to contribute to society.”
It is also useful to tell a story, such as something life-changing. Make sure that you explain what you learned from your experience and how you plan to utilize that knowledge.