Need a system to organize my jobs and studies

Hi, I have a hectic life and am struggling to organize and remember everything I have to do. In short:

• I am in med school which is pretty intense.
• I work as a research assistant and have multiple work-streams with tasks that must be completed within deadlines.
• I work with risk management in a fintech with three different subsidiaries in three different countries. For example, I must remember to create document X for country x and y, and update it for country z. For each subsidiary I have a long list of tasks that must be done.

I am starting to have problems with organizing and prioritizing all the different tasks. I have some control in med school in that I try to attend all lectures/tutorials and usually spend two to three hours at the library after all the lectures to review and take notes. I have tried to use a simple todo list but it gets way to chaotic.

Would greatly appreciate input on any tools I could use to help me.