I don’t want to be rude or anything, but it seems like you did do something wrong, and if you did that you get slapped in the face with a game over. You screw up? You get a game over, its how it works. I get that you are frustrated, but this game was never meant to just rush through,
The other acivities are not useless, they add to other hidden variables. Most players don’t see the game over screen because they take their time, don’t want to get Alice fat asap. For the longest time I didn’t know anything about hidden variables. At the start of the game you should focus on being a good boyfriend
So like other people say, that means being romantic, taking her to the cinema, going along with her choice. When she watches a movie at your place you can say she is prettier then the woman in the movies, take her out to dinner on saturdays and pay for her.
Reading this will probably frustrate you more, which isn"t my intent at all, I realize that many have said these things before. My point is just that, the games story is build up so brilliantly, it should not have to spoon you all the answers, otherwise Tigger could just remove all choices and have a visual novel without any options at all.
However, I hope that you get to experience the game after the game over screen!