If you do the quests, you'll get development materials from doing those. It's why you want to prioritize unlocking fleet 3 and 4 as soon as you can, so you can do more quests.
Ships can only be sunk if you continue a mission after a battle where a ship is in the red. Basically the kanji/chinese for "BIG" means you don't want to battle. If you accidentally do go into battle, just quit your browser ASAP as you can usually cancel out of a battle that way.
I think the first few maps of world 1 are relatively easy. World 1-4 becomes hard because they introduce carriers and you don't really have a counter until you get your own carriers and battleships to at least try to counter them.
Also, use Kancolle Viewer if you aren't already. Even if you can read the Japanese, having access to all your information in a simple manner makes life easier than using the flash interface.