By Martin Baccardax “We expect Q2 to have both lower transaction volumes and lower (Monthly Transacting Users) than the Q1 levels,” said CEO Brian Armstrong. Coinbase Global (COIN) shares plunged lower Wednesday after the cryptocurrency trading platform posted weaker-than-expected first quarter revenues and cautioned that activity would likely continue to slide amid the ongoing upheaval in digital currency markets. Coinbase said revenues for the three months ending in March fell 35% from last year to $1.17 billion, well shy of Street forecasts, as retail trading volumes fell 38% to just $74 mi…