Can I use External layout to create pause menu on the same scene rather then go to the new scene? Will it have a different time then the current scene? I want to pause the scene and to have a pause menu. I want the time to be paused or scale down to a small value, rather the to disable through variable because then “trigger once while true” is creating problem?
i didn’t used for a long time, but you can just load a scene “menu” ON the current scene ; the background scene will be paused in the meanwhile. Actions : “pause and load a new scene” and " stop and go back to previous scene".
I wanna be able to save game by doing so!!!
It sounds like you misunderstand what an external layout is. It is not an independent scene or anything like that.
Once you create something from an external layout in your scene, everything from the layout become part of your scene from that moment so if you pause the scene, everything created from the layout will be paused too at least in the current stable release of GDevelop. I believe the latest nightly build got the feature to pause layers individually so you can pause only the game layer and create the pause menu on a separated layer… Mind you, nightly builds are unstable and very likely going to corrupt your project.
when they are releasing new version of GD. Please give me some good newz 
As far as I know there is no release date and it seems to me the release of the new IDE become priority before anything meaning no new release is planned before the new IDE is done. Even the nightly builds have been stopped probably because Victor got no time and 4ian is busy with the IDE 
Maybe we can get 4ian or Victor to comment on this.
What you can try though with caution is use a nightly build only to add the pause functionality and export the final release of your game. But I don’t recommend to use the nightlies for development of your game but only to attempt to add the pause functionality at the end. Before open your project in a nightly, always create a backup as it might just corrupt your project any moment…
But really I think your best option is what Kink suggested. Whatever you want to do on the pause screen can be shared with the game scene through variables and storage actions. For example if you want to equip a weapon on a pause screen (similar to Fallout 3 for example), you can just save it in a variable or storage what weapon is equipped on return to the game scene…