What are some ways to learn finance?

I would recommend taking 2 courses from Prof Aswath Damodaran

Corporate finance which is management way to look at companies
Valuation which is investor way to look at companies

Basic principles for finance
1. Time value of money
2. You should borrow money in the same currency as your expected cashflow
3 how much u borrow and how long u borrow should depend on the stage of your company and the projects u taking.
If u are a loss making start up don't borrow money
If Yr projects are long term don't borrow short term

If you'd like something more structured, there are tons of Massive Open Online Courses (MOOCs) that are free to use to increase your knowledge. Although the credentials aren't recognised, but putting these in your resume would also showcase to employers the dedication and commitment you have in picking up new skillsets.

The Google of MOOCs

https://www.mooc-list.com/

Individual offerings

https://www.edx.org/

https://www.coursera.org/

https://www.wallstreetoasis.com/

https://www.futurelearn.com/