Slavery in Africa
Slavery existed in Africa before the slave trade.
If you were owned by an African slave master there was a 50 50 chance that you would be treated reasonably well. If you were owned by an Arab master you were most likely to be treated well because in Islamic teaching they taught that they should be kind to everyone.
If your parent was a slave and you were born there is a chance that you might not become a slave.
You could work your way out of slavery or the kingdom chief of where you come from could buy you out of slavery