How the fuck do you memorize 💀

Not sure if this is just a defect with my own brain, but I learn shit only for it to fall out of my head in 1 zeptosecond 💀

I can do physics, ochem, calc, and gen chem pretty well. I can also do psychology to a degree since it involves some reasoning. Now biology? Hahah I can learn it for the purposes of the exam, but it's out of my head in 2 hours max.