This didn't happen in chapter One, til then, everything was fine. How to fix it, because I tried to play again, and it's always the same.
How to fix it?
As Claudius mentions - you don't "fix it".
The Sorcerer doesn't "memorize" spells - they just replenish available spells per level (when resting).
The specific spells are only chosen at level-up. So perhaps you select Fireball as your first 3rd level spell, and then later (when you level-up again and get another spell to select) choose another 3rd level spell like Displacement.
The only time you "loose" spells (other than casting the amount you have allotted for that class level per rest period), is if your main attribute is altered OR if you loose character levels.
For a Sorcerer - Charisma is the classes main attribute, a 12 in Charisma gives you a +1 modifier, a 14 gives you +2 (etc..).
At some point your attribute modifier starts adding too, your spells per day to cast based on rest period. So the higher the Sorcerer's Charisma the more additional spells per level you'll be able to cast.
Something that lowers your Charisma (like a curse) could remove spells to cast (per rest period), though again not any specific spells. Remember you need a base 11 in Charisma to cast 1st level spells, 12 for 2nd level, 13 for 3rd level, etc.. So if you get knocked down to a Charisma of 12 then you loose access to any spell above 2nd level.
Also, level drain effects (negative levels) would remove spells to cast by lowering your character level (..and thus access to spells available at higher character levels).