Welcome to PsychCentral, Proust!

This is going to sound like terrible advice, but just keep practicing. Practice writing essays. Something I do to help organize my thoughts is to just start writing things down. Not sentences, nothing fancy, just ideas. Once you have some ideas, start organizing it into an outline. And once you have an outline, you can start filling it in. When it's in the outline stage, you can move things around, change the order of paragraphs, etc. until it feels right. I hope that helps!

I'm terrible at math, so I can't really help you with that... All I can say is practice there too, but beyond that...

Good luck!