u/Acoasma

So I climbed out of the depths of Germanys third division and managed to play in Europa League and Champions League for the past three seasons. I did slightly increase my max wage each season to keep up. Currently my highest earner is making 40k €/w and I am looking for upgrades for next season.

As my left wing back is getting old and I need a replacement there I found this gem, which would be a significant upgrade for only 12.5m in transfer fee. However, he demands a huge wage in comparison of ~100k €/w even with maxed loyalty bonus.
I would really like to sign him, but I have a feeling it would completely screw over my finances, as probably half my squad would demand updated contracts in no time, ballooning my wage bill which is currently sitting at 930k €/w altogether.
On the other hand I am still sitting at roughly the same expenses as the bottom teams in my league.

I am extremly unsure how to go about it and wether i should prioritize getting a wonderkid that is a perfect fit or rather keep my wage structure in tact.

How do you guys go about situations like this? what would you do in my shoes in this situation? What are your general guide lines for wage structure and its development when climbing from lower leagues to (hopefully) the top of Europe?

I have this guy who is in fact a decent AM that can also jump in as F9. However, I got better players now and he won't be getting much game time the coming season, which is why I offered him in the transfer room to see what i could get for him.

This upset him and as he is a highly influential player I was like "fine, you can stay" - planning to just phase him out, hopefully bring his influence down and offload him next season.
Now I got a really good offer for him after rejecting the first two and I would like to accept it, but I am worried that it could just piss him off and he wont accept the contract, leaving me stuck with an unhappy highly influential player.

Anyone knows how this will play out?

Those players are playing their respective positions for easily 10-20 games if not longer and are also set to train their IP and OOP role in individual training. Still they don't seem to reach full familarity and I don't understand why.

What are the most common mistakes that lead to this? What else can I do besides letting them play the role and train in their role?