I have lost my ETH. I want to know what could have gone wrong.

Here is the transaction. https://etherscan.io/tx/0x35bb1a312b59703cfd7077f0b0e28ae3c9b6caad4fa9b78a355ebd35e71cee11

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1. I am using both MetaMask app and Web3 app. I know I shouldn't but I couldn't afford to buy a hardware wallet yet.
2. I have stopped the iCloud autosaving feature after MetaMask asks everyone on iOS to do so. This news. Could I be too late to do that?
3. I did not approve any smart contracts.
4. What should I do now? I still have some ETH on the CEX.