Some questions on ethereum proof of stake

Hello,

I just wanna ask some questions on ethereum proof of stake mechanism. So, I understand that there are validators which validate transactions, and that you need to stake some amount of coin to become validator. More coin you stake, more validating transaction and more fee you will get. If you don't validate transactions fairly, you can be ,,punished,, by taking some part of your staked amount of coints, or even everything you staked. Now, the questions are:

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1. How exactly validators validate the transactions? It's not that they are sitting at their pc pressing yes and no button?
2. How can someone cheat and validate corrupted transaction?
3. If someone stakes on pool, and validate not valid transaction, does the whole pool takes damage?

Thanks for your help.