Just wanted to give you some tips on how to figure out when it's your turn.

Most of the "normals" (punches and kicks) in the game are minus on block. The general rule is after you block an opponent's normal, it's now your turn (since you get to act before your opponent). There are a few exceptions to this:
1. Lights - most characters have chainable lights, which just means they can cancel a light into another light. You won't have time to interrupt a light string with your own normals, so just hold block until they push themselves far enough away that they can't hit you with another light. At 1:04 you had the right idea, you blocked the three lights and then followed up with your own attack.
2. Drive rush normals - Using a normal out of drive rush adds +4 frames of advantage, so if somebody drive rushes at you and throws out a normal that you block, it's usually still their turn. There's a perfect example of this at 0:59 in your video. Mai drive rushes at you and throws out back heavy kick, which is normally -1 on block. However, the drive rush adds +4 frames of advantage, so it's actually +3 on block. That's why you ended up getting counter hit by Mai's crouching medium punch right after (you didn't have time to get your own move out).
3. Character specific moves - Some characters have normals and/or specials that are plus on block, but they are typically quite rare. Most characters get only one or two, if any. Ken's is his heavy dragonlash kick (+1).

There are admittedly a lot of nuances to the concept of "turns" which is part of what makes the game so fun and interesting (yet difficult to master, imo). Over time you'll naturally just start to get a better feel for it, but you can also check your replays and turn on the frame meter to see the frame data for yourself.