Can someone give me some tips of how to study. i have already tried writing everything in my lesson but it doesn't seem to work

Highlighter, color coding sections that go together, flash cards, relaxing with someone while they read out questions ( this will help with testing anxiety too). If you get distracted easily use games to study or small sayings instead of the usual white and black sheet of paper.

The independent variable would be the fertilizer as it is what the dependent variable (the growth of grass) depends on.