1 month means a year in the game?When do the players stop playing?

A month in real life actually means two years in the game.
So, A player ages twice a month.

At the age of 40 the player retires, and the team will get 85% of the player's value.
U cannot put a player above thye age of 34 on the transfer market.

Thanks.One last question:Can i sell them in half price or I cant?

Yeah. U can sell em at half price
But if u let them retire on their own, u ll get 85 % of his value.