How to increase my daily sales volume

Hello, I guess this is my sharing my story about my FBA journey so far. I started the professional seller account in May of 2021 so it’s exactly a year since I start this whole thing. I was doing my research and just as soon as I opened up my seller account my sister introduced me to this guy who apparently makes 50k per month in FBA sales and that he would be a great partner to teach us both (she had started her own seller account at around the same time as me) about how to source the best products etc. She spoke so highly of him that I completely trusted the person like he was per of the family. So we start working with this guy and she sends me a great looking product that he would like to source for me to sell on my account. He said this product- a lingerie set- would be a great starter product and I’ll need to pay about 36k to get about 5000 pieces of this really hot selling item. I thought it was a lot of money to send to someone who I barely knew so I called my sister to talk to her about it. She said she’s good for the money and that he makes so much more than both of us combined that this is peanuts for him. She Eve said she had already wired him about 50k for 2 kinds of products that he has already ordered for her and is on the way. She said she would pay me my money back if anything went wrong and that I should trust the guy. So I stupidly wired him USD 36k for 5000 pieces of lingerie set. I really didn’t think it would arrive and that the guy scammed me but to my sure it did. I have been able to start selling it online but It’s just so much that it’s taking forever to sell. I am doing all the thing I can like the campaigns and everything but my sales are still very low. What can I do to increase my sales volume?