Hello
I agree with the capacity if save goods. 480 for each lvl is not enough.
If you are a veteran player than you lust have some basic knowledge how to defend you'reself. And the're are plenty of options. Build a wall and place a ship and some troops in you're city. Make some friends and ask them for help when needed. If you want to save you're goods you can use cargoships to transport big amounts of goods. And send 1 million rescources to another city. And they navigate the see slow so you can take advantage of that. You can also send you're enemy a message and talk you're way out. You can also build a small fleet or army. More generals means safety. Since generals scare you're opponent.
Last resort is gravejard but I don't recommend it since it takes a lot of time to get settled again on the good Islands and most of them are full.