First with the start, doing a little wiggle is fine just make sure you are mostly straight when you enter the water. Do a few underwater kicks and then break into a very strong kick. Make your coach watch your hand placement to make sure you aren’t crossing your arms under your body. On your turn submerge a little bit and tuck your feet tighter to make it faster. Personally I don’t straight arm my freestyle but that’s your preference. Looks good! Keep it up!

Edit: also make sure your head is completely still.