Well, nowadays lvl 6 trainer is almost affordable. Kind of like lvl 5 before that. But when you started training him, lvl 6/7 trainers were really expensive if I remember correctly. ;)
The 4 Mio arena design is probably helpful, but I only upgraded in Utopia and only for about 1 Mio (if I remember correctly). Now I don't have the money for another upgrade, especially since you'd have to get 4 mio even if you already put 1 mio into the design ...
Good luck with everything and yes, the NT team might get into shape. Our German team kind of is a rebuilding process, especially after our successful team manager quit after losing the World Cup Final (which was very close and in our opinion, we should have won^^) ;)
Winner: 1x Consolation Tournament (U21), 2x Goldene Ananas, 1x Goldene Himbeere, 2x Goldener Erdapfel, 3x Bronze Medal (U21)