Simply download and sideload the new version. Your save game will be intact as long as you don't delete it yourself.
Edit: I should mention that you need to sideload the same way (either via web or usb) that you did with chapter one as the game directories are named differently on device depending on the method you use.
The save that I supplied is far from a "perfect" save, but does leave you with plenty of food and a few rocks iirc. While I applaud you for getting through C1 without using food, it is there to be eaten 😅
If you do need to use the save file for any reason, instructions are at the bottom of this post.