How long it takes to change resident status

I am pakistani i came to japan as a temporary visitor on 1 may 2018 my brother invite me and after one month i got married with a permanent resident she is living from 30 years in japan holding a very good record in japan working two jobs one is care giver and other is food company we applied for change of residents status after completing all important documents and process we applied for change of status on 20 agust 2018 then after one and half month immigration send a post to us that we need the wife tax certificate we send it very immediately but still its already two months and 3 days but still we are waiting why it take so long i hear that spouse visa i mean change of resident status take 4 to 6 weeks and in rare cases it take 2 months but in my caese it take 2 months and 3 days and still no result out we call immigration many times tbey says only wait little more can any one tell my about this situation something is any chance of rejection in my case i am 23 year old and my wife is 54 year old but she is still good and healthy and young workinv two jobs thank you in advance

Three months, not 4-6 weeks.