Thanks for your answer! The application is called Bitcoin wallet (it is the first suggestion on Bitcoin.org). I was trying to have the same wallet on two different devices (not sure if it is a good idea). I have only a small amount but I would like to make a transaction with my phone if I get a chance.
This one?
https://bitcoin.org/en/wallets/mobile/android/bitcoinwallet/While it is listed on bitcoin.org it isn't compatible with a Bitcoin Core wallet.dat file. It has it's own wallet format (it uses the BitcoinJ library if I'm not mistaken).
In any case, what you're trying to achieve isn't readily possible when starting with a Bitcoin Core wallet. As far as I'm aware, there aren't any Android apps that support reading a Bitcoin Core wallet... and you can't get the seed out of Bitcoin Core, only the master private key. Then you'd need to find an Android wallet app that allowed you to import from an "xprv". Personally, I think you would be best off finding a wallet that is supported on both PC and Android (like
Electrum) rather than attempting to clone a wallet from one app on one platform to a different app on a different platform.
From time to time the transaction fee is high to transfer funds from one wallet to another.
True, fees have spiked again... so I can understand your reluctance to want to move funds right now... but it is highly likely that they'll drop back down to 1 sat/byte in the not too distant future. If you have no immediate need to access the funds (and don't mind waiting for a few hours or a day or so) you could simply send the transaction with a 1 sat/byte fee and just wait until it gets confirmed. Or just wait until the fees drop and then move the funds.
