Establish Cost Basis For Crypto Purchases

I started purchasing cryptocurrencies on Coinbase in early 2017. A few months later I opened accounts with Gemini and Poloniex among other exchanges. I traded transferred gifted and made purchases with my crypto. I discovered this year that I overpaid my taxes because of inaccurate cost basis for my sales/purchases. I need an expert to reconcile my transactions and establish an accurate cost basis. This is a big confusing job that requires an expert.