TurkPilot,
Impact does have to do with kinetic energy but GS is only relevant if you are impacting the ground.
I ‘ll give you an easy example so you could understand it.
Two aircraft are flying towards each other and have a TAS of 500kts each. With 0 wind and therefore 500kt GS they have a closure rate of 1000kts.
Same scenario with 100kt wind. First aircraft has a GS of 600kts and the second 400Kts.
Closure rate 1000kts. In the air GS has no affect on closure rate. The only thing that shifts is the point on the ground that they would cross.
If you are training for your PPL and they are teaching you all this crap I suggest you change flying schools.