Did Hana Hana no Mi give the user superhuman strength? Hana Hana no Mi is eaten by Nico Robin, as we know that she can grow parts of her body.
She usually grow her hands to attack, or to defend her. She also can swing or lift her or other people with her growing hands.
She can easily break the bones of her opponents, just like when she used clutch or twist.

I know that if her body parts are hurts, she also feels the pain. But is that mean when she used clutch or twist, she used her "normal" human strength?
Because she doesn't seems no trouble when do that to her opponents. Or it's because the Hana Hana no Mi that also give her superhuman strength?
If you are asking whether Robin was given superhuman strength by the fruit's powers, the answer is no. The duplicated limbs she creates are no stronger individually than her normal limbs.

To quote the One Piece wiki's page on the Hana Hana no Mi:


  The strength of the user is also still limited to their individual strength, meaning that the individual strength in the replicating appendages is no different to that of Robin's actual corresponding limbs. 


However, she can get around that by creating multiple limbs so as to subdue larger people or move heavier objects, as she demonstrated during her fights against Yama and Oars, among others, but even then she has her limits, as she noted how heavy Yama was during her fight with him. The fruit itself doesn't make her any physically stronger, she just uses her powers creatively to make up for her weaknesses.