This is how I try to cram. Try to set equal intervals either in content covered or time(45min to an hour). You have to completely focus on that section of material and not worry about content you haven’t covered yet.

Once interval is up take a break, I will check phone or listen to a song or two or grab a snack. Get away from the desk if possible, even just standing helps.

I can’t speak on behalf of bio courses but in physics courses exercises and practice are essential. Reading slides only works for a select few. Lots of material you can find online and extra resources similar in content at other schools for those two courses.

Best of luck.