Dcentralized exchange that are based on smart contract are very safe! Smart contract can not be changed which means the moment you execute a trade there is no turning back or manipulation. Your address lock your trade and it is impossible for your trade to reverse!
Yes they are safe. Your funds are on your wallet or on your wallet in contract. There is 1 option that you can loose it. Correct me if i'm wrong. When decentralized exchange is hacked code written in contract can be different (instead of exchange funds will be transfer funds to hacker accout). And if you are not able to check if code written in contract is correct than you are not safe.
