1.Constant breaks, varied revision methods, e.g. split time between reading notes, writing notes, doing questions
2.Try a site called memrise, for languages duolingo is also good, but more for general improvement.
3.Reading books in Spanish, using sites like memrise/duolingo
4.For maths+science, topic revision then practice questions, self-mark and things you got wrong will stick, repeat. English, make sure you know the mark scheme so you know what you need to include in your essays/analysis/creative writing, and practice
5.Chill, but you can also try doing enjoyable things that are educational, like watching Spanish shows with english subtitles on Netflix.
6.Have in your mind what you're doing when, e.g. 10-12 maths, 0-2 break, 2-4 physics, 4-5... It doesn't have to be a schedule, you can just mentally pre-plan at the start of every day.
7.To improve knowledge, watch documentaries around your topic, for memorising events and event sequence, make mnemonics, for dates you can use memrise, practice essay questions structure.