Good hustle, I like that you use the overhead stroke for the rear court backhand side most of the time. Agree with both points, sometimes your serve is also a fault because you are touching the boundary lines. You stand too far in front, your base position should be more like just behind the white line. At 0:59 you get caught out because you're not behind the shuttle, taking it side on and too low. Other times it's an issue is 2:08, 3:23 and 4:35. Your footwork is okay, if opponent was hitting full court then it needs to be faster. I'm not good at identifying if someone is using panhandle but I think so since your lift is short. To help this you can also follow through like you do on high serve. Short lifts are also making it easy for the opponent to smash. Yuta Watanabe is 167cm (5'6") and weighs 56kg (123lbs) and Hiroyuki Endo is 172cm tall and 72kg. The reason I thought you are around 20%+ is because your BMI is technically overweight, no offence intended I'm just using the standard reference ranges. However if you consider doubles they tend not to be as lean with a greater variety of body types, just aim for something you feel healthy at. If you find that trying to lose fat is leading to decreased energy for badminton training then it isn't worth it, however it's really simple to do just by eating less and continuing to exercise.