Just switch off all technology, and rid of any distractions, and set times for when you have to study for a certain subject and once youve completed that time have a break go back on your phone, reward yourself until its time to study again
Motivation is temporary. Drive is what keeps you going. If you don't have motivation to do a certian topic. Sorry but hard truth is you rely on motivation which comes and goes in order to help you keep going.
As a teacher of Biology for 20 years, I recommend short bursts of study regularly. Keep up to date with current topics, but also keep going back to earlier topics. When you feel you have mastered each topic, tick it off and don’t revisit that topic as much. Agree with previous message, motivation is nothing without goals and drive. Make studying fun! Use Quizlet for interactivity with technology and learning Biological terminology, create lots of diagrams that represent processes. Study in a small group of 2-3 of driven students to keep each other motivated. Reading big slabs of text is not so useful. Review notes and make revision notes that summarise content.
Anyway, I could keep going but wish you all the best with your studies. Access to Quizlet content for Unit 3 and 4 if you want it. I have the entire year of topics set up.
Unit 3 - https://quizlet.com/andyjamespiper/folders/vce-biology-unit-3-2017-2021?x=1xqt&i=4lofl
Unit 4 - https://quizlet.com/andyjamespiper/folders/vce-biology-unit-4-2017-2021?x=1xqt&i=4lofl