Currently, i haven't beaten the first boss yet, i don't know how to finish this snail thing...
hey! The design wasn’t too obvious but I tried to show it during the boss’s entrance cut scene. Basically you have to reflect a boulder with your shield, which will make the snails tongue stick out, then you whack the tongue with your sword. I can’t remember how many hits it takes but it’s either 3 or 6. Good luck. Hope this helps.