Wish + would is used for complaints - I wish heīd stop that! ( but heīs unlikely to); I wish she would behave ( but as a rule, she wonīt)
Wish+ simple past is used when one wants the present to be different.
I wish I were slimmer(but Iīm fat); I wish you were here( but youīre not); I wish I didnīt have to work today but I DO!
Wish+ past perfect is used when you want the past to be different!
I wish I had studied harder for the test! ( but you didnīt, and you failed it!)
I hope this helps