Any thoughts on self taught who, i'd think, has a seasoned understanding of time complexity but lacks meaningful mathematical notation background necessary to use Big O fully?

Which is to say i have no confidence issues in my working knowledge of Big O. I lead a team, i've developed obsessively for 10 years now and despite my many short comings i don't think understanding trivial complexity - the why of "Why is HashMap faster than BTreeMap on lookup? When is it slower?" etc - is lacking. But, i couldn't use Big O notation to any meaningful complexity with any real confidence. My math background is nil.

In general i need to up my interview game, which i think also means i need to up my math game to have a firm understanding of Big O notation itself.. but the complexity is not the issue, for me at least.