Hello, landlord. First of all, it takes 1-3 months for bones to harden. The effect varies from person to person. Skin is useless because its function is to protect meat. Hard bones depend on one word, practice more and play more. Tap the stick gently and gradually increase its strength as time goes by. Finally, your bones will harden. It is best not to drink carbonated drinks during bone training, which will only soften the bones.