When I smile, the flesh at the corners of my mouth squeezes together and creates a long wrinkle, just like the wrinkles an old man shows when he smiles. How can I get rid of it...

These two wrinkles are called nasolabial folds, which are a type of dynamic wrinkles and will be clearly visible when smiling. The reason is that when facial expression muscles repeatedly contract, they squeeze the surface of the skin to form wrinkles. You are just 14 years old and will not show symptoms of skin aging, so if you want to get rid of nasolabial folds, don’t make too many expressions.