How do I defend myself. Was just attacked and 4300 killed. He had 0 killed?

Defence is a matter of having more troops, researching your combat and troop skill trees, building up the Garrison and Tower buildings etc. to improve your city. You can also use various buffs such as a defence bonus item from the store or alliance store to temporarily increase it if you are under attack.

Unfortunately if you are being hit by a much higher level enemy then you will still be vulnerable and likely to lose. You can stop attacks completely with shield items. 8h, 12h and 3 day shields are available in the store for diamonds.

In some cases the best defence is to send your troops out of the base (gather, attack far away zombies etc) so that when the enemy attacks you only risk losing some resources (if you have them) and don't lose troops.