When using wish, the tenses ‘go backwards’.
Although the wish is for something now, use the past tense.
|I wish I don’t have homework.||I wish I didn’t have homework.|
|I wish she is my girlfriend.||I wish she was my girlfriend.|
|I wish I can do magic.||I wish I could do magic.|
Wishes in the past have to use the past perfect tense.
The past perfect tenses is had + done/eaten/gone etc.
|I wish I studied harder when I was at school.||I wish I had studied harder when I was at school.|
|She wishes she didn’t kiss him.||She wishes she hadn’t kissed him.|
|He wishes he didn’t get drunk at the bar and acted stupidly in front of the staff.||He wishes he hadn’t got drunk at the bar and acted stupidly in front of the staff.|