Before you can get to the bottom of why your withdrawal is taking a while, you'll first need to check what the status of it is on the Withdrawal page under Withdrawal History:
If Transact Status doesn't say Completed, You can use this guide to figure out where your withdrawal is and when it will be completed.
If your withdrawal has been Completed on our end already, and you haven't received it yet, it could be because the transaction is currently unconfirmed on the blockchain. You can check whether that's the case by entering the Transaction ID shown on Withdrawal History on a Block Explorer.
How long will the transaction take to get confirmed?
The time it will take for miners to confirm your transaction on the blockchain will depend on the fee paid and the current network conditions. You can use this third-party tool to see an estimated wait time per fee paid - https://bitcoinfees.earn.com/
What if the network is congested?
Unfortunately, in certain network conditions, like congestion, transactions can take hours or days to get confirmed. It's also and especially the case if they were sent with a low fee compared to the current requirement.
Rest assured that your transaction should get confirmed eventually, it's just a matter of time.
Is there anything I can do?
Once your transaction has been broadcasted, there isn't anything you need to do as it's a waiting game at this point.
If you would like to speed up your transaction, there are Bitcoin transaction accelerators (through 3rd party sites) that can help with that.
You can also use this third-party tool to see an estimated wait time per fee paid - https://bitcoinfees.earn.com/