I'm not sure if it's fair to directly say my ex-manager was not supportive. So I'll describe my struggles and feedback at my previous job first.
I changed jobs a few times after graduation to be able to get a more technical role to build up my foundation (along the way I also signed for a few courses) and finally I got to the buy side to do financial analysis from a marketing background. In the interview, I made it clear I had no financial modeling experience but I was really keen to learn and I passed the basic modeling test (I took online course). The fund manager gave me that job but in the daily work my direct manager's approach was to throw me different work assignments without initial walking through and previous example. She said she wouldn't hand in everything on a plate and I needed to think. I guess it made sense and so I started my work. I would consult Google if I can't figure out some formulas and did trails and errors to find out the best approach to do an analysis. Then I got the feedback that I was way too slow. When I explained my approach, she said why you didn't ask me questions in the first place but instead to go ahead and do trails and errors?? It's a complete waste of time. But for me, I did't even know what to ask in the first as I never did that before. I only figured out which parameters to look for when I tried a few times.
So this situation went on for a while until they officially let me know it's not a match for both sides and ask me to resign.
My questions are how should I explain the reason I left my previous firm in the interview? And should I keep looking for similar function or I better find a new function that I may be able to prove my value easier?