Crypto market has shown bull and bear cycle in very short span of time. From rising from 10000 usd to 69000 usd and from 69000 usd to 16000 usd in span of around 2.1 years I think it is fastest reversal of any new tradable market.
Double top means making almost two equal highs and failure of bull to make new high while bears pressure of continuous selling makes this pattern.
Neckline is where bitcoin has taken support as seen in chart.
Generally target from top to neckline is expected in double top.
Let us see whether bitcoin makes new low from now to reach target as marked in chart.