I'm 22 years old and probably need to spend another 3-4 years to retake classes
It will take a little more than 1 year. 2 Summers, Fall, Winter, and Spring.
thats how long it took me to retake gbio, gchem, ochem, physics, calc, a&p, calc, + random grade boosters. i left my undergrad with a 2.384 so with your 2.5 you seem to have a better starting point.