People should feel free to add new information, but this question has been answered before:

https://www.reddit.com/r/AskHistorians/comments/24jgyf/why_did_german_fighter_aces_have_so_many_more/ (top answer by /u/eidetic)

https://www.reddit.com/r/AskHistorians/comments/33yvrs/why_did_the_wehrmacht_and_luftwaffe_have_so_many/ (top answer by /u/Domini_canes)

https://www.reddit.com/r/AskHistorians/comments/3ixxop/why_did_germany_have_so_many_fighter_aces_in_ww2/ (top answer by /u/barath_s)

It's a number of things, but basically boils down to target rich environment. You can only shoot down planes if you encounter them. An American pilot could fly 50 missons without seeing a German plane. The Germans were outnumbered and could expect to encounter enemies wherever they went. At the same time they had the initiative, their presence decided where air combat would occur. Which then tended to be at terms locally favorable to them of course.

This was compounded with Geography. Western allied fighters had to cross Seas and countries to fight the Germans, so lots of transport time, in the East the air bases had direct contact with the front and air combat was possible from take off to landing. And with this closeness to the enemy the German fighters regularly flew several combat missions a day. If an allied pilot was shot down over Germany they couldn't be rescued, while the German pilots fought over their own territory or in close proximity to friendly ground forces which meant that they had a good chance of immediately being recovered. The Germans also had a chronic lack of pilots which meant that they couldn't rotate their experienced pilots when they completed a tour as the allies did. Their aces flew until death or wounds incapacitated them.

You might be interested in Gunther Rall answering your question https://youtu.be/STFdRrWBW2w?t=68 He was the third most high scoring ace in history, despite spending 9 months of the war in rehab with his back broken in 3 places.