With hard training you lose in average 18%, can be less can be more depending on the player, but the gainning is not 30%, tha all depends of the player, one fast trainer between 18 and 21 can gain 160%, 80% in normal training, a slow trainer with the same age can only gaine 50%.
In friendlies the loss of condition can be between 13 to 16%, less that on normal game, and you can change all the players, and win boosters.