i already have downloaded the 0.6V but when the 0.7V comes how to do i update? do i have to completely download as new? or is there any way to update
What blasphemy...
You should absolutely replay the game! It is way to good to be played only ones!
But don't worry, the savefiles should be saved not in the folder but... Idk... In appdata or in the registry or somewhere? Anyway's, after installing the new version and launching it if you didn't reset your pc or somehow deleted those files as well it SHOULD just show your saves. But no warranty given if you completely deleted the game xD
The update procedure for Windows, for this and most other RenPy games (RenPy is the game engine in which Eternum and many other games is running), is:
1. Check your Eternum saved games folder, in Windows it's located in this path:
C:\Users\YOURUSERNAME\AppData\Roaming\RenPy
where "YOURUSERNAME" is your actual user account name. It might be a hidden folder, so you might be required to check the "Show hidden folders" option inside Windows file explorer.
Inside that path, you can see all saved games from all your installed RenPy games , each one will be inside a folder with the name of the game, "Eternum" for this game, along a very long number.
That's the folder where your saved games are actually stored, they aren't stored inside your game folder but in this other one. The reason for this is to separate game data (which is generic, and should be easily replaceable) from user data (which is particular to you, and only you can replace it). I don't agree with this architecture, but it's the one Windows is following since Windows XP times.
Make a backup of that folder, in case something goes wrong, because you could download the game as many times as you want, but you can't replace YOUR saved games if they get corrupted, erased or broken somehow.
2. Extract your downloaded 0.7 version game to a different folder from which 0.6 version folder is in. Exactly like you did when you first installed the game, but to another folder.
Don't mix folders from different game versions unless you are told to. Other games release an "only update" version and a "full release" version so you aren't required to download the full game again just to update.
Eternum was only a "full release", so the new game folder doesn't require being intermixed, the new release is everything you need to run the game from the beginning and to continue from 0.6 .
3. Open the new 0.7 version exe and go to load game. Here there would be two possibilities, depending on:
a) The new version being incremental, which means 0.7 contains 0.7 and everything backwards, including the start of the game. This is how Eternum worked until now and I couldn't run 0.7 yet but it's probably the same. With 0.7 version you can just load any saved game and continue playing from there, when you reach the end of 0.6 you will just continue with the new 0.7 content.
b) The new version might not include previous content, which would probably be announced with a "Second part", "Season two" etc... name. For this, you need to save the game at the end of the previous game where you are told to, "Please save your game now" or the like. Then, when you start the following version, you won't be able to start from the start of the game because the new version doesn't include previous content, but you would be able to "import" or "load" the saved game you did at the end of the previous game and continue from there.
4. If you downloaded an incremental version, which is the case with Eternum, once you checked you can continue playing the new 0.7 version content, you can delete the 0.6 game folder. You can safely delete it if:
-You are sure you backed up your saved games folder, described in step 1 here
-You are sure your 0.6 saved games work with the new 0.7 game, so you don't need to keep using 0.6 version for anything else
5. From now on, you can always start the 0.7 version game. It will keep the new saved games in the path described in step 1.
6. For future updates it's the same procedure
Hope it helps, this kind of install procedures were usual for older games (pre Windows XP times) but aren't common now, so if you never found one then you won't know where to start.