[Suze65]

I agree with Mrs frog ( Jackie ) and I used to have one of these torts.
He/she will be just fine in your walled garden for the summer with the house you have got him.
I personally would be inclined to let him have a short hibernation , so long as his health and weight are good by September. But don't worry about that now, you got time to do more research .

Just let her settle in and relax ( that's you ) make the changes to diet slowly.

That's what I would do