1- My bookshelf can-----------only 100 books whereas you
have brought 200. (Is take OK?)
I would say
My bookshelf can accomodate(contain,include) only 100 books whereas you have brought 200
2- Haven’t you been shaving? Why is it(your shave) so----
(Are big and small OK?)
I don’t like this sentence at all Shave is not the appropriate word.Maybe you imply bristle or beard?
As Pamela said, accommodate would be a possibility. You could also say hold. (I would not use contain or include — I assume Pamela simply mentioned those words to clarify the meaning of accommodate.)
Like Pamela, I don’t understand what you’re referring to here (“your shave”). Do you mean your beard? Your razor? The cuts on your face from the razorblade? The “five o’clock shadow”?