delete Tennis.ini (or the .ini of your Profile if you created one) ; you'll have to set again all of your parameters, but after that it may work correctly.
If you created a Profile, re-create it after that with the exact same name to access again your saved games.
Many Thanks for the quick reply!
If I delete tennis.ini I lose everything, either if I delete also profile.ini or if I don't.
If I delete only profile.ini I don't have to create another profile with the identical name because it creates automatically.
So I just deleted profile.ini and now the situation is pretty improved: now, among the best player, only Dimitrov is from Andorra and I solved also another bug I did not mention in the previous post: when I started the game it took a lot of time to load the main menu, 30 seconds more or less, while the rest of the game was at normal speed; now the loading is fast as it was at the beginning.
Sadly I still have a few bugs: sometimes, inside the menus of the world tour, it seems like the enter key is continuously pressed and I cannot do anything except playing the match or restart the game.
And my player, federer, is still blonde haired...
If you know any ways to fix more the game fine, if not don't worry, it is fully playable after all.