Let's see if it's possible.
What is Dapp?
- It's basically a decentralized application running in multiple computers to verify transactions, etc.
Would the owners have access to your key?
- No. Probably the Public-key is the only thing they could get.
- Unless different attack vectors have compromised them, you are probably safe.
I'm not very familiar with smart contract and what can Smart contract can do to secure our assets
Basic rule. If you don't understand the terminologies and new technologies could offer, don't use it. You might regret it later.
I don't even know where or how to check source code. I mostly read app review instead
You know reviews can sometimes be bought, right? It could lead to other things you might not expect. I think you should be careful.