Your transaction has 54307 confirmations. That's enough confirmations for your ETH to be received on your Bittrex wallet. Are you actually sure you sent the ETH to the right address? If so, I'd contact Bittrex support[1] right now.
The network is severely congested. So that would be causing a delay in the transaction appearing in your Bittrex account
How long ago did u send it?
OP is talking about Ethereum, not bitcoin; which is definitely not severely congested.
[1]
https://support.bittrex.com/hc/en-us/requests/new