You can withdraw bitcoin from Bitstack to any other Bitcoin compatible wallet at any time. To do so:
Tap on the ⬆️⬇️ button in the app
Enter the amount of bitcoin you want to withdraw
Tap on Bitcoin Address
Scan a QR code or tap Send to enter the recipient's BTC address
Tap Continue to verify your withdrawal details
Tap Confirm
You need to withdraw at least 0.00050000 BTC or 50,000 sats (satoshis) to initiate a transaction.