Thank you all Sawarane & markantonik , it's been a great help
Your tips are very useful and easy to follow and i found I've done much better than before with "transpose line", honestly, I don't think I'm 100% get the control of those 3 circles but it doesn't matter I still get what I want for a few tries.
I hv tried using "Dynamesh", I'm not sure if i get this right but is that the purpose of it is "redistributing the polygons" so I can get more polygons to control of the ear(a particular area)
My situation is after I hit "Dynamesh" two things happened, looks like the details at the point of the nose are gone as well I cannot edit the mesh again (shown something like I have to "Freeze the subdivision level" but then I can't "Unfreeze it")
Is there anyway I just add polygons on particular area(like only on ears) and not affecting other part of the body?
I've tried close the lips and shorten the neck in the same manner,i t works well but the thing is there are cracks between where the polygon meets. There are other places that a small slope/valley are formed after transpose but they can be solved easily with "Smooth" brush. What should I do to merge this polygons without distortion? I've looked for some video teaching how to merge two meshes but don't find anything that seems suitable for my situation(one mesh), Thx in advice