It’s unfortunate that you lost money on your trading, but there was nothing that went “wrong” with BTG. Variance in block find times is normal; it’s a stochastic process. Here is the current chart of average block times for April for BTC, BCH, and BTG, from BitInfoCharts:
All three of these chains have average 10-minute block times, and all exhibit variance.
Even if every block took exactly 10 minutes to find, your deposit would have taken just over 1 hour and 40 minutes for ten confirmations (Bittrex requires ten confirmations, plus both exchanges require some time for processing and approvals). In your case, you had the bad luck to have two very slow blocks in those ten, so the confirmation took longer than avearge - but short-term variance should be expected. It might have also confirmed more quickly; this is just luck. If the systme is working properly, the average will be close to 1 hour 40 minutes, because the average block takes close to 10 minutes.
The average block time is close to ten minutes, as designed - actually, based on the graph from BitInfoCharts, we’re actually running a bit fast. That haveing been said, we’re looking at ways to improve our DAA to acheive our 10-minute target while minimizing variance despite the competitive GPU-hashing market.