It's a question that they ask me a lot, it can be before, after, even as a snack, it all depends on your goals and also on how your routine is during the day.
I usually take it before the exercise because breakfast at 8:00 in the morning, I take the shake at 6 PM, I will train and then I eat my dinner, it works for me, you have to see how it works for you too .
If you are looking to increase muscle mass I recommend two shakes a day, one in a fast prepared with water because it helps to break the catabolism of the night, at half an hour you have a normal breakfast, and another shake after training to increase protein synthesis and affect muscle recovery If you are looking to lose fat or stay with one a day is enough.