The transaction most likely was dropped from the mempool due to the fees being too low when this happens block explorers also remove the data reason why the txid is not assessible. Sending small amounts of bitcoins to the same address does not hasten the initial transaction. Ask the sender to confirm if the bitcoins has been returned to their address.
Some wallets allow one to bump the fee after broadcasting. You can also use RBF, where you send the exact same output but with a higher fee.
thanks for your answer
the question is, i have the money on my wallet (the sender said he hasn't gotten it nor can he see the transactions on his wallet), will it become useable? What will happen to the money of both transactions as i have it on my wallet but can't use it?
How can i use RBF for future?