... is that all the teams are totally different after just a season, it's so unreallistic! I mean, what team in the world should sell all their players and buy new in just a couple of weeks?

You're so right. Especially in the Danish league: Some teams would by and sell 20-25 players within the first two months. I partly solved the problem by using an editor to change some of the teams from semi-professional to proffesional- but I agree that there still is far to many transfers. Sometimes a player is transfered 2-3 times within one single season.