How long does a transfer take
Transfers in bitcoin can take anywhere from a few minutes to a few days depending on the network status and the fee paid. Currently, it's closer to a few minutes. In either case, you can also usually view unconfirmed transactions in your wallet or on block explorers such as blockchain.info.

In your case, however, things seem unlikely. All such apps that I've ever heard of (free mining, free btc, etc.) are scams, and never actually pay you. They will simply claim the withdrawal is pending, or keep telling you that you are under the withdrawal limit, while using your device for ads, or other purposes.