Masks come in many sizes and not all masks fit all faces. To test the fit,
place the mask on your face without using the head strap and making sure your hair is clear of the mask skirt. Inhale slightly through your nose. If the mask stays in place for 30 seconds or more, it’s an ok fit. It it falls off you face sooner, try a different mask.
Choose a snorkel with an adjustable mouthpiece which should help with how it fits. Some snorkels have a design on the barrel which prevents water from splashing down the barrel. Others have a purge valve to help stop that first breath of air to not fill with water.