I have no idea what i'm doing

I found a random tortoise in my street a few days ago about be attacked by dogs so I picked it up and brought it in and asked around to find the owner, no one knows whos tortoise it is. So it looks like I now have a pet tortoise but I have no idea what i'm doing. I don't know what type of tortoise it is but i assume its a Sulcata as i live in Cape Town South Africa.

I've been keeping it in a washing tub with some water and lettuce to eat but it doesnt look like it's eating. It's cold...

I have no idea what i'm doing