could you please tell me what yellow leafs mean when appearing on leafs?
thank you

The yellowing leaves could be from over or under-watering, or, the light is not right, maybe too low, or seasonal, when higher light becomes less. Mine will lose a few leaves in the fall to yellowing,, then a few more will yellow in the spring when the light intensifies again, then it stabilizes and does well all the rest of the summer.
Pothos do well in bright indirect light. Water thoroughly, let it run out drainage hole, empty excess. when all the soil has had a chance to dry. No fertilizing in the colder months. Also it's good to check leaves and stem once in a while for any small pest like spidermites or mealies as the leaves can yellow or become speckled.