Keep your outside shoulder lined up with his inside shoulder. Make sure he stays out on his circle and doesn't get closer and closer to you. Keep his head turned towards you so he gets in a nice frame and headset :)
I'd really recommend watching ArttoRide's videos on youtube on lunging. Basically you want to create a triangle with yourself at the apex and the lunge line and whip creating the sides to the horses mouth and hidquarter respectively, with the back of the horse as the triangle base. The whip should always be present but if he reacts strongly just keep it low and trailing bit still in position and following until you need to give a forward que. If the horse is falling laterally in then point the whip to his shoulder, giving a little shake if he doesn't react immediately. But turning in is an evasion of forwardness - as soon as they start you have to quickly step forwards towards the hind (this itself is a very strong aid only used if needed) and tell them to keep going on with the whip . Young horses generally react strongly to the whip but with time they become accustomed As they begin to understand exactly what you want.
I use my whip in a motion towards him along with the verbal cue "out" to get him out. If he gets out of control on the lunge line ask him to slow, I then put my leading hand up in front of him (right hand if he is going to the right) then if he doesnt respond begin to step in front. If he turns away use the line to bring him back. If completely out of control slowly reel in your line to make him go in smaller circles until he slows and stops in the middle! Hope this helps ❤
he’s still young and likes to come in to the center unless I have a whip he will know what to do but he just goes so fast on the lunge line so I don’t like using a whip but when I pick it up he will know what to do if that makes sense