

Well, population density does that, I guess! Not much to be done about it, even in other parts of India with population not as crazily dense as Mumbai.
Between that and avoidable traffic jams created by vehicles blocking intersections, cycling may be the fastest method but also needs breathing more polluted air. But the time overhead of public transport can’t be reduced with this population density. So … a rock and a hard place!
Would the Delta Chat e-mail client or the Monocles Chat XMPP client help? They both support webapps-in-chat (WebXDC), and a calendar is one of the many simple apps already created. https://webxdc.org/