Wala namang problema kahit i-import mo pa private keys mo sa etherdelta. Your private keys stays on your browser and were never sent to their servers. Kaya safe yun.
You might have accidentally entered your private keys on a phishing site like a Phishing MEW Website.
Baka may nakakuha na ng private keys mo.
Better check your transaction history. See if saan pumunta yung precious token mo.
https://etherscan.io/address/0x01c68DE2A7A84BF0A58797C53aa91F08cF2A6cBf#tokentxns
Palitan mo yang naka-bold ng inyong ethereum address to check it.
Always remember, if you're using MEW (MyEtherWallet), .com palagi yan, not anything else, to avoid phishing sites.