Other financial discussions

This thread is pretty helpful, however, what I have gathered somewhat confuses me in regards to my auto loan payments. 

 

For a 5 figure loan, my minimum payment began at $350/mo for a 3.3% rate starting November of 2017. I have steadily paid $550 each month since I started and my minimum payment has been $0 for a while. Obviously I still have a balance and my payment has not changed, but that doesn't necessarily mean my $550 is 100% principal right? How is the principal/interest payment calculated then? Am I only paying interest at that point and a really good chunk of my payment is principal now? I guess I just really don't understand how my lender changed my min. payment from $350 to $0.