My dad have bladder cancer of 4th stage

I am sorry we are not doctors here. You need to seek a second opinion at a major center that does a high volume of bladder cancer. You might ask them about a possibility of a clinical trial. I am sorry we can not help more but know we hope you find some during your second opinion.

I am sorry you and your family are in this situation. If I were you there are two things you will want to consider.
The first is to consider hospice for your father they can help with his comfort and help the family with his care and the emotional storm this is causing in your life's. Doing this soon is important for all of you.
The second is you might if your father is well enough get a second opinion from a large center who deals with a lot of bladder cancer. This will probably not change anything but if might help you knowing you had done everything possible.
Again I am sorry this horrible disease has effected your family you will be in my heart and mind.