The further apart the current values are from the future values, the less accurate the future values are. Each player has a secret attribute that pushes their future values to trend in a certain direction - most players it's negligible, or goes up and down throughout their growth process, but you will have a lot of players that will trend upward or downward. If you have a player that is trending upwards you probably want to keep him around; if you have a player that's trending downward, then you probably should be wary about locking him to a long-term contract until he peaks out his skills.

Your coaching staff is responsible for closing the gap between current and future - so a better coaching staff may reduce the amount that a player will lose.

The cap used next year is whit the Dead cap?

"Cap used" is the total of your player salaries for the next year, and does not include the dead cap.

What is short medium long in this game?

Designation of play types that can adjusted in the gameplay settings. I feel those words are generalization of play types. When used can give you limits of how far the play will most likley go. But, by no means is it a result that is set in stone.

A better example might be if you play a D which sports a cover 4 might be weak against an O that passes shorter. Favoring situations like this can enable a team to play well when applied correctly. Its more about a way to apply your scheme.

But in offence when the playbook say 2 short or 2 medium How much yards to go is short medium long

JDB says it in more detail in the blog under help. I see it changing based on scenerios played prior. I believe this is were gameplay adjustment comes into play.

Here is the referenced article:

http://blog.myfootballnow.com/2015/03/short-medium-and-long-what-do-they.html

If i don't want my head coach but is contract is for 3 years for 6 000 000, do i have to penalty if i fire this coach?

nah. but what league?