This game is about economics. You need easy and cheap victories, while giving none yourself. Don’t buy transports if your dad will sink them easily, you would be better holding one turn for a following turn larger purchase or buying aircraft. For Germany, hit where you have the best chance to win and take the most cash. Use the NO’s to guide your grand strategy. But other posts above are correct, there is a tipping point where all you can do is slow down the inevitable Allied win. There are some good posts here that can guide your next game.