What is the best coin to buy?

Getting a wife, 2 spouses contributed 500 million to invest in Altcoin. Every month I save a little, at the peak it reached nearly 800 million but I didn't take profit, now the assets have dropped back to only 300 million. It has gone without a word of farewell. In fact, it has even gone negative on the capital.
What should I do now?
Cast out to USDT and wait for a downtrend to enter again or still hold the current altcoin$ETH ? Thank you everyone
{future}(ETHUSDT)
$BNB
{spot}(BNBUSDT)
$SOL
{spot}(SOLUSDT)