I am not having any problems with training and have not had to modify the qsp. It is possible that you have missed training and you did not get the option to say your grandfather was sick (need appearance to be >300 for it to show.)
If the option does not appear then you are permanently locked out of the swimming training chain. You can check if this has happened by using qsp save editor and checking if npc_unique_trener_pool[6]=1. If it is just change it to =0 and you can ask for training again next visit - just make sure appearance is always over 300 if you miss a training session otherwise you get locked out again
wait, how do you open the save with save editor in this game, it doesent create a .sav file or i atleast cant find it
probably, i got the option to lie but without tinking i chose the other one, but as i said i solved it by modifiing the qsp anyways.
the only thing i still cant solve is the kiosk owner and the continuation to the trasure quest, on the last one i did every step until you have to go into the archives. but when i ask about the archives i get a lot of weirdly tranlated nonsense that i understand as
"no you cant look into the archives" even tough i have best friend with the girl.
but as i said, done all the steps until there. read about the treasure. talked to grandpa, went to the collectionist.