I always see runners leaving the shop as soon as they buy the roundabout and then buying the lobber on the screen closing animation, how? It will save a couple seconds if I know how and thats precious time wasted lol

If you buy the roundabout and leave the shop at the same, the closing animation will play but you will still buy the roundabout. The timing can be a bit tight (especially since you gotta make sure to not exit before buying). During the animation there is also enough time to buy the lobber.

Just press the buttons for buying and leaving the shop almost at the same time, with a few practice you will get used to how to do it pretty quick