Jim Cramer recommends speculative buy for nLIGHT, Inc. due to recent OTA agreement. Duolingo announces Q2 results and stock rises 6.1%.

"Mad Money" host Jim Cramer rings the lightning round bell, which means he's giving his answers to callers' stock questions at rapid speed.

Jim Cramer recommends speculative buy for nLIGHT, Inc. due to recent OTA agreement. Duolingo announces Q2 results and stock rises 6.1%.