Two weeks ago ,he told me that he discovered that my hot wallet lost 59.788 bitcoin within 1721 transactions between 2016 to 2020 and the scammer is the Bitcoin ATM manufacturer that sold me the POS terminals.
Certainly you should sue the scammer. However, people will definitely ask how you didn't notice that someone stole your BTC. and they stole it very slowly. 1721 transactions? This doesn't look like what a scammer woudl do.
A scammer would just make one transaction to steal all your money. Something is wrong in this story. And you realized only 5 years later??
I know that 59 BTC didn't have the same value as today during 2016, but at the end of 2017 the value of 1 BTC was as high as $20k - so it's not clear to me how you didn't notice that you missed so much BTC over 4 years?
I think this is a good point. They didn't stole you 3 million USD, but much less. In 2016 bitcoin was not even 2k USD... anyway, that is still a lot of money.