there is no way he have access to my private keys but i am reading some weird things and wonder if is possible.
Care to show some examples the weird things you have read? I think you are having a misconception about most of it.
if some one knows my both wallet address and time of the transaction; any how can that person do something about that transaction? steal, hack, freeze the account etc?
during the transaction or after?
ETH enforced OFAC-compliant block, if your fund is somehow tainted with bad stuff that violates some regulation, it could be censored. Do also note, some stablecoins have a feature to freeze funds, so it is another possibility. Overall, A general or even the most sophisticated hacker can't do much with only the address and time of the transactions.
First of all I would advise you change wallet from a third party based like Coinbase as that is a third party wallet which can turn offline any day and you can forget about your coins as that saying says "Not your keys,not your coins".
Coinbase Wallet is a self-custodial wallet, as they have claimed. So as long OP keeps the seed phrases secure, it should be able to be exported to other wallets. Also, Coinbase Wallet is not a third-party wallet, I'm not even sure what you mean by a third-party-based wallet.