Can anyone help me to see what I did wrong?

Instead of grabbing, try and wrap yourself around the joints in some way to pull him closer. Also try and hit the joints more directly, and if possible at the end don't try and grab the head, and kick the neck instead. Hope this helps

For the first punch att: Try contracting your pecs,wrist, and elbow till you're at a close enough distance and then extend wrist, pecs, and elbow and rotate you're chest as well.
Result below

Btw nice opener