well, i don't know if this is the correct way to update the game or not. but whenever I tried to update the game, I always download the new update file without deleting the previous version file. after I download it, I extract the new version file and go to my previous version file to copy the save data (go to your previous version folder. after you get into the folder, click the game folder and there will be a folder that written save. copy them all and go to your new update file and paste the folder exactly in the place where you find the save folder in your previous version folder)
there are some games that the developer decided to give the player the update file so they don't need to install the game again, but it's not applied to any game as far as I know and I could only find one at the moment.
hope this helps