hmm, i can see that your sources (boosters) are limited .
money too.
So you can't keep many young fast trainers and develop them much so we must be careful where to invest.

- GK no, never invest to a GK trying to keep him in high q or many seasons.
Just buy a simple 5* GK, cheap, and replace him every season. He won't be ever a "key" player.
GK's performance just reflects the team's q and performance or the roll dice (good/bad day) of one game.

- It's good to have a "defensive wall" and a "header" sa in your roster.
Da Silva (DR) has the "wall", he is young fast trainer but he is only 4*-5*
Fuaud (DL-DC) is also a promising one but still is a 4-5*
The same with Kukic, The other DL defender. fast trainer but 4-5*.
Do not invest to the other two defenders (the 20 y.o.)

- Fournie, the DMC is a fast trainer.
- Soucheski the MC is a 1st class fast trainer.
- Bojang no (but he is a good performer)

The other attackers are fast trainers.

The problem is that your team is young and expensive but you don't have a big roster and you 'll have problems to keep it healthy (injuries and condition)

You must cover your budget so must sell ST-AMR Feher and buy 1-2 old, cheaper players.