This is what made it click for me, can recommend it:
3Blue1Brown -- But what is the Fourier Transform? A visual introduction.
3Blue1Brown -- But what is the Fourier Transform? A visual introduction.
Reducible - FFTs the most ingenious algorithm ever https://youtu.be/h7apO7q16V0 Veritasium - The Most Important Algorithm of All Time https://youtu.be/nmgFG7PUHfo