hi guys, i have the following problem.
I work on two computers, one at home and one in the office.
I create part of the game at home and save it with a name, I save the game on a USB key or send it by e-mail.
When I open the game from the computer in the office a lot of components, sprites, platforms, enemies etc. they are not present, they disappear. Why does this happen?
Hello, GianLuca 
Are you copying only the Json file? Or are you copying the entire folder of your game? Are you saving the new sprites in the game folder or out of it?
@Rasterisko
This is a good question you ask me …
I only save the json file …
what should i save to have the whole game on two computers?
If you are saving your sprites, songs etc in your project folder you can just put that folder in a pendrive and open it on your other computer, because the folder will have your json file and all the new files you created.
So, are you saving your files in the project folder?
@Rasterisko
I downloaded Gdevelop. When I use Gdevelop online it makes me save to a folder. When I use the version I downloaded on the PC of Gdevelop it only saves the .json file
Where can I find image files and others?
It is actually you who need to tell me where the images and sounds of your game are saved on your computer. 
I have no experience with the online version so I can’t help you with it.
With installed version, if you are using Piskel to make your sprites they will be automatically saved in your game folder.
If you’re doing your sprites with other software or downloading it, you needs to know where you’re saving. When you load an image on Gdevelop to make, for example, an animation for your character you need search for it in your computer, right? So… where is it? 
Use File/Save as to export your json file along with all the required assets.