If you want to leave Tradish for good, the Delete Account flow removes your account and your data. It is built to be clear and deliberate, because deletion is permanent. As the screen says: "This permanently deletes your account and removes your synced data from every device. This cannot be undone."
The flow spells out what happens when you go through with it:
There is no undo, so make sure you have anything you want to keep before you start.
Deleting your account does not cancel your subscription. The flow reminds you: "Deleting your account does not cancel your App Store or Google Play subscription. Manage it in the store to stop future charges."
So if you subscribe to Tradish Pro, cancel in the App Store or Google Play first, then come back and delete your account. See Managing your subscription for the steps.
Two things are required to finish:
Once you confirm, your account and its synced data are removed from every device.