Most of the Altcoins are in a clean downtrend on daily timeframe.

This is how you can evaluate if the trend is shifted or not.

Go through the daily charts and you'll see price creating lower highs and lower lows.

When Bearish Trend Breaks?

You need to wait for the price to break the lower highs streak on the daily chart. Once it does, You should shift your bias from bearish to bullish and look for some swing trade opportunities based on the daily chart.

why High timeframe only? Because it provides you the most accurate picture and results

I have attached the examples for your better understanding.