On the Ethereum network, in order for a transaction to go through, miners need to approve it. Since miners collect gas fees paid by the sender, they usually look for transactions with the highest gas price to approve first. That is why lower gas price transactions take longer to process. In a pool of many transactions, some transactions with the lowest gas prices never get picked up - miners are not willing to process them. It results in them getting "stuck" in a pending status. There are two things that can be done to resolve a pending transaction (same process will work for multiple pending transactions, one by one):
Resend/recreate the transaction:
The order of processing of transactions is determined by the value called "nonce". If you want to resend the transaction that is "stuck", you need to determine its nonce value and create a new transaction with the same nonce value. To find a nonce value of the transaction, simply click on the pending transaction and find a field called nonce. Record the value in that field (a number). After that, create a new transaction (with your original "Recipient address" and amount). On the confirmation screen click the "gear" icon in the top right corner, scroll down and replace the nonce value on the screen with the value recorded earlier. Set a high gas price. Confirm the transaction.
"Cancel" the transaction:
In order to cancel a transaction, you need to do the following. Click on the pending transaction and find a field called nonce on the screen. Record the value in that field (a number). Start a new transaction. In the "Recipient address" put YOUR OWN public wallet address (the same one you are sending the transaction from). For the "Amount" put in 0 ETH. On the next screen, click the "gear" icon in the top right corner, scroll down and replace the nonce value with the value recorded earlier. Set a high gas price. Confirm the transaction. This process will create a new transaction that will override the pending transaction and cancel it out.