Guide for smooth transition from bitcoin.tax

Describe the problem:
I have three years of data 2017 to 2019 on Bitcoin.tax. I’m wondering if I can just import the closing position from Bitcoin.tax 2019 and only import transactions since Jan 1 2020 and still get the right calculation? This way I don’t have to bother with the thousands of transactions prior to 2020 and save money. Note that I do have transfers between wallets and exchanges.

Which exchange/wallet is this regarding?
Bitcoin.tax

How did you import data into this wallet?
Downloaded the csv for 2019 closing position and imported to Koinly.

What have you tried to fix this so far?
I just want to know if this can work or not.