Duolingo's stock cratered 27% on lighter-than-expected guidance as the language learning platform zeroed in on user growth in lieu of near-term monetization."We have made a slight shift over the last quarter in how we invest, and we're investing a lot more in long-term things because we see that as such a big opportunity ahead of us," CEO and co-founder Luis von Ahn told CNBC's Jon Fortt.For the current quarter, Duolingo expects bookings to range between $329.5 million and$335.5 million, falling short of a ...