I have a prototype game, and i realice that in the instalation of gdevelop there is a game with the same idea 
Can i use this game with some modifications and publish it in playstore? Or it’ll give copyright problems or something like that?
Examples are there to show you how to do things but some of the examples are developed by members of the community and 4ian asked for permission from the authors to include them with GD so depends on which example you are talking about, but I don’t think anyone would care if you use the example but better if you contact 4ian about it.
But really, any example comes with GDevelop can be done in few hours or less if you know what you doing…
In case you need the sprites and sounds comes with GDevelop, probably you can use them as 4ian including only free sprites but even if it free, it require to be licensed so always better to get permission/license directly from the author.
Again contact 4ian if you want to know where you can get the licenses from…
Some of the sprites and sounds you can find it here published by the authors under different licenses:
opengameart.org/
Always read the licenses before use, some of them can be used for free, some of them can be used only in free projects.