Is one sinful for adding to the original expenses of online lectures to cover the cost of a computer device, under the pretext that this additional amount is part of the lecture expenses?

Being keen to learn is good, but it is not permissible to lie to your father by increasing the expenses of lectures to buy an educational device. Rather, you must inform him of the purpose. If he agrees, then praise be to Allah. Otherwise, be patient and fear Allah until He facilitates it for you.