There is a dua I read called Dua-E-Ahad and it is said that if you read it 40 mornings in a row you will be among the helpers of the imam and if you were to die before the reappearance then Allah would rise you from your grave to help the Imam.

1) What time exactly do you read the dua during or after fajr? What if you run out of time to read the dua and fajr is over will it count or will you have to restart?

2) If I miss one day I don't have to start counting from day 1 again because I've been struggling to read 40 days in a row? And if I were to miss one day is there any way I can make up for it so I don't have to restart or do I not have to restart in the first place

1) You will continue with the dua after salat. You don’t have to restart

2) Restarting is definitely better if you can. If not, you just pay the day back and continue