Pending Transactions in Electrum
Check confirmations on blockstream.info

If unconfirmed, open the wallet where you had sent, spend those BTC by sending to another address in same wallet with a fee rate more than what others are paying. Check mempool here: https://mempool.observer

This is called child pays for parent transaction: https://bitcoinops.org/en/topics/cpfp/

If unable to spend those unconfirmed BTC, there will be an option in Electrum settings which you need to enable