Since your Class Time is a constant rather than a variable, I think it makes sense to prioritize Learning Quality first. The more you can learn while you’re part of your professor’s captive audience, the less work your Study Efficiency will have to do later when you’d rather be hanging with friends and playing Fibbage (the best party game ever, I might add)
The first step to upgrading your learning quality is deceptively simple: Pay better attention in class.
This is one of those “easier said than done” pieces of advice; semesters are long and classes constantly wage a war of attrition against your motivation levels. These strategies will help you weather the storm.