Evidently, this is from the Basic English Bible (BBE), not the more common King James Version.
If you find out how to switch your app to the King James Version, though, you're bound to find some linguistic oddities there, too. Language has changed a lot over the past 300 to 400 years. Whether you read Shakespeare, Chaucer, or the King James Bible, you can't expect it to sound like contemporary English, which is why more contemporary translations have been written.
The Basic English translation may have some grammatical oddities as well, but for very different reasons. It was deliberately written with very few basic words; it's essentially a "Green Eggs and Ham" translation of the Scriptures.
As for why it was translated as "At the first" and not "At first", I'm guessing they wanted to retain the three-word prepositional phrase construct, but for some reason thought "In the beginning" would be too difficult for its target audience.