I don't know why I'm wasting my time, as I'm sure this has been answered a dozen times and I doubt you care.
There's no such thing as a "beneficial" mutation in and of itself. A change occurs, that's all a mutation is. If it doesn't kill the organism or interfere with the reproductive success of the organism, it'll be passed on to the next generation along with other new mutations. If these don't kill it or interfere with its ability to breed, then they'll be passed on, in addition to other mutations, and so on.
Over time mutations (change) continues. Its a continual process, because God's organisms are imperfect in their replication process. Its why we can grow better and strong crops, why we can breed dogs into all manner of sizes and shapes, and how organisms can adapt to changes in the environment. Sometimes the changes don't help an organism reproduce or kills it, so that it doesn't pass on those traits. Sometimes changes allow it to be more adaptable to the environment it is in, so it will become more fixated in the population (increase in allele frequency) of organisms.
That's it. No magic beneficial mutations. Just ones that don't outright kill the organism when it reproduces, or causes it to survive better in its environment. Organisms constantly change when they reproduce, and environments constantly change as well. Evolution is just the mechanism that allows life not to die out when the environment changes.