In case of you don't receive any webhooks for a transactions you can use a polling mechanism.
Polling refers to the practice of repeatedly querying a server or endpoint at regular intervals to check for updates or new information. This is in contrast to using webhooks, where the server notifies the client when there are updates or events of interest.
You can use the https://developers.u4c.com.br/reference/get-charge-by-itemid to check the status of a cashin transaction, and https://developers.u4c.com.br/reference/get-transfer-by-id to check the status of a cashout transaction.