As your other post about backgrounds, in which you provided the same example shot you would like to emulate, and I offered suggestion of how it was likely achieved with craft not kit; in that instance using forward focus to pull the DoF zone closer to the camera, where AF would struggle to find something to actually focus on, with more floor bricks infront of the girl in focus than behind as back-ground oofed.
In days of yore, it was suggested that a very mild telephoto, around 80-120mm on 35mm film, perhaps 150 or 180 on Medium format, was a 'Portrait' lens, as they begged backing up a certain amount to frame a subject, and so offered a more 'flattering' perspective that didn't so easily make noses look huge as reletive distance between the tip of the nose and the eyes was a much less significant proportion of the camera to subject distance.
B-U-T as your query about the back-ground and subject and what red-dot scheme to use; that 'nugget-of-know-how' is just that; its why a lens of that angle-of-view 'may' be better for portrait shots that 'may' be more appropriate for those sort of situations, that gear does not 'make' those situations or necessarily grantee the best result; its the knowing how they work and why they may be more appropriate that makes the difference, and with that know-how, and more, using it to pose your subject, not directly facing the camera so that there is such a difference in distance between eyes and nose, and they aren't looking straight at the camera like a prison mug-shot.
Its not the kit on your mitt, its the craft in your cranium...
There is no 'best' or 'worst' lens for portraits or street candids or anything else; only better or worse ways of using one... and THAT is what I think you 'need', not another lens; a shift in outlook to NOT expect the hardware to do it all for you, but a greater appreciation of how to make the hardware you have help you do more of what you want.