Hi, I'd like to reassure myself on one point ... Is the percentage gain from group training really random? I know it changes every season but there's no way of predicting or influencing this percentage!

Let's say it revolves around a fixed value determined from the coefficient of its season (mainly) and the level of your EA at +- 3% approximately, it is that this last part which is random, a blow it is more a blow a little less, but on average considers that it is fixed over the whole season.

Galywat: Disons qu'il tourne autour d'une valeur fixe déterminée à partir du coefficient de sa saison (principalement) et du niveau de ton EA à +- 3% à peu près, c'est que cette dernière part qui est aléatoire, un coup c'est plus un coup un peu moins, mais en moyenne considère que c'est fixe sur l'ensemble de la saison.

I'd also like to add that the progression coefficient can't be known in advance unless it's his last season of training, in which case you just need to do potential - (day 1 progression status + progression coefficient) which gives us the coefficient he'll have in his last season.

إذا كنت تقصد معرفة النسبة المكتسبة للتدريب الجماعي للاعب معين للموسم الحالي نعم يمكن معرفتها لأنها شبه ثابتة فمثلاً هذا لاعبك T. Galasek
نسبة زيادته في التدريب الجماعي تكون 30.63% وبما أنها شبه ثابتة فقد تزيد او تقل عن هذة القيمة بمقدار 1% في كل جلسة تدريب ,أما بالنسبة لمعرفة نسبة زيادة التدريب للموسم القادم لا أعرف IF YOU MEAN TO KNOW THE PERCENTAGE GAINED, PLEASE CONTACT US
If you mean to know the percentage gained from group training for a specific player for the current season, yes it can be known because it is almost fixed. For example, T. Galasek
this player's percentage of increase in group training is 30.63%, and since it is almost fixed, it may increase or decrease from this value by 1% in each training session. As for knowing the percentage of increase in training for the next season, I do not know.