No, if this is the tortoise you brought into the country then you need to use top soil. Garden soil can contain small stones etc which will be detrimental to your tortoises health.
Have you taken the tortoise to the vets for a poo sample to be taken to check for worms?
Wild caught tortoises are reknowned for having worms and if left untreated will cause serious problems and can lead to death.
Then I suggest you get it to a vet as soon as possible, I understand that this may be difficult because of the circumstances it was brought in under but for this tortoises sake you really need to get this tortoise checked.
I know this as I have recently dealt with over 100 wild caught tortoises seized at Heathrow - worming is extremely important!
You need to have him checked out, also I would use a mix of top soil and sand. Or you can get bed a beast or eco earth which is cocnut husks. It works great and you don't have the dirt smell.
You need enough water to cover the bottom side of his shell (plastron).The water should be luke warm.I use a cat litter tray to bathe my torts,and let them stay in the water for about 20 minutes.I bathe my small torts daily.Dont leave your tort on its own in the water,keep your eye on him incase he tips up.