Train or sell

[Mitja fc]

Hello
I am pretty new at this game and I am wondering what would be best to do in given situation...
I got a player from youth academy that looks like this

My main striker looks like this



And my best offensive player looks like this



I have a feeling that my striker is ****...he is 19y old and when i train him alone he gets like +1% gain at cca 12%-15% drill he gets more when i train him with more players tho is this normal btw that players gets more % if group trained 4 players for example compared to train 4 different players solo ?

My winger is monster tho...he do have average star rating but thats due to low def stats but he doesnt really need any does he ? And he do score a goal every game more or less...

So I can spend cca 200 greens shall i train or sell the young prospect? He gains around 6% if trained solo per 12%-15%