Self-learning via books. I've bought a bunch. Am currently going through Susskind's Theoretical Minimum Classical Mechanics [1], also looking through No Nonsense Classical Mechanics [2].

AI chatbots sometimes come to rescue when I am stuck. Not with mathematics though.

[1] https://www.amazon.com/Classical-Mechanics-Theoretical-Georg...

[2] https://www.amazon.com/No-Nonsense-Classical-Mechanics-Stude...

Awesome! By the way, there are also books that accompany the first three courses:

https://www.amazon.com/Classical-Mechanics-Theoretical-GEORG...

https://www.amazon.com/Quantum-Mechanics-Theoretical-Leonard...

https://www.amazon.com/Special-Relativity-Classical-Field-Th...

If you get the first one, make sure to get the one titled 'Classical Mechanics' and not just 'The Theoretical Minimum' as the former is a more recent printing with many corrections.