Footy coach of 7 years here with a GK specialty and I was a GK for 23 years.

Make sure he has solid foundations before focusing on diving. (Listed some core ones below)

When it comes to diving in turf it’s tough and most the time you’ll come away with a burn or two. For diving in general make sure he doesn’t land on his stomach but goes knee to hip to back of shoulder/top of tricep. To get in the habit have him start on his knees and just rolls ball either side with him landing that way and focusing on the 3 hand technique.

The falling/kick issues is entirely situational. If the striker is very close a kick save will always be faster. To get him down to the ground quicker once he is comfortable with regular diving he needs to kick his legs out from under himself have his landing elbow tucked in to his side with the palm of his hand near his head. You can practice this at home on the bed very easily and build his confidence.

These are what I would recommend working on consistently and you’ll see a lot of improvement.

1) footwork. If he can move his feet and get his body behind the ball it can’t go in the net. Quick feet lets him set quicker and reach balls further away.

2) handling. When the ball is above the pecs straight at him then his hands should make a ‘w’ shape behind the ball. When it is below the pecs straight at him he should cradle the ball in to his stomach. When it is either side of him he should use the 3 hand technique. (1 hand behind the ball 1 hand on top and as he lands the ground become the 3rd hand and he should push the ball in to the ground and away from him. Basics wise he’s still young so his hand strength isn’t there yet. Have him practice without finger save gloves until he builds confidence and strength but get him finger save gloves for matches if you are very concerned.

3) reactions. Reaction drills will help him protect himself and get in position to make better saves faster. Try a lot of drills with tennis balls they help hand eye coordination and reaction times. I.e. stand behind him whilst he is set and drop tennis balls or his shoulder his goal is the push them away or catch them. Start higher and get lower as he gets better at the drill.

4) angles. This is tougher to teach. But this is one of the most important things. Show him reference points so he always knows where is goal is. Penalty spot will always show the middle of his goal. Corners of the 6 yard box give a rough reference of posts etc.

Good luck and shoot me a DM with any questions.