ok so you know what other people have said so far. mkae a checklist an check off things as you improve them.
The only thing i will add which i dont think anyone else has picked up yet, is that your upper arms should be dropping straight down to the ground, when we stand naturally n the ground our arms stretch down, not with our arms forwards like we're pushing something..
you also look like you hanging on his mouth a bit in saome of the pics, coming from you being tense in your hands and holding them too low. rememebr there needs to be a direct line of contact going from the horses mouth to your elbows :)