3 years as seller but still failed

Need help, I started as retail arbitrage ( to understand how Amazon works) i got most of the big brand approvals sold items from retail stores or wholesale markets then I started buying products from Alibaba and listed , few of listed items got reported by other seller and few are not selling well.

How to find right products ?

If I find something and start selling, someone will report to Amazon saying it’s there product. Some products get old.

Need help/ suggestions to find out how to find products that can be stay longer and make profits.