hey man! first of all, i've tended to drift off in thoughts aswell. Simply correct that when you find yourself drifting off and start over. after some time doing this, you are going to be more focused on the things on the outside, instead of focusing on them in your mind. So if you see a tree, it wont be like - you see a tree - nice tree - i could make a treehouse in it - what if that tree would be bigger -. Nope! Thats just your imagination talking. Try to be more like - nice tree - its very big - its leaves are very red - i can see a butterfly on the tree -. You're more focused on the aspects of the tree that are ACTUALLY there, instead of imagining things around the tree that COULD be there. If you correct yourself while you notice that you drift off to your imagination, stop and start over! after some time, you will notice that you are looking very critical to your surroundings without really imagining things around them that are not really there. It will be tough at first, but soon it will go automatically!

How many minutes i can get done:
Let's take our tree back here. I could practically look 10 minutes to a tree and focus on its aspects what makes it a tree, but that will get boring and you will drift off to your imagination no matter what. If we take a couple of things in one area like a trashcan, a car, a tree and a couple of people, i can ADA on them as long as im in that area. I first did this by forcing myself and just having a really bad time, but now, in that same scene, i could choose between ADA the surroundings or let my imagination have fun.

I think, in the first week, i practiced ADA, forcefully, 10 times a day with a length of 2-3 minutes each session. In week two, i tried to keep on to 5 times a day, same length. In the third week, i skipped sessions. I tried to be aware to whole day, so that was my aim. That turned out to very long periods of being aware, and some moments less aware. I tried to be ADA without forcing moments to do it. It worked out pretty well actually . I now dont do sessions aswell. I only ask myself at the end of the day i was aware enough throughout the day. The sessions are just to let your mind think it's become a new habbit of you - looking critical to everything. Soon your subconscious will take this habbit over and its ingrained. When you lose the grip of this, simple go back to sessions a day and grind ADA in your subconscious again!

your last question.
yes and no. In the beginning, it took a lot of focus from my daily routine stuff. But the better you get, you wont even notice that you're ADA-ing and doing your normal day routine things at the same time. You will be just aware of what you're doing, without forcing yourself too much. And that is of course what you want, cus it aint fun to waste your day with forceful ADA'ing.

I hope i helped some here! Good luck with the ADA practice! You can always ask if you got questions, peace