depends on the visual novel, but some visual novels they work like this:
First time you read it the text shows in slow way or it even follows the voices of the characters (this can be configured in the settings most of the time) but after you read it it will be displayed in 1 time giving you chunks of text at the same time, it is a way to show/inform you that you have already read those lines, a game that uses this method is fate/stay night for example.
Can you fix this after reading those lines? nope, the only way to fix it is deleting the save file that the visual novel auto generates (not the save file you create)