How can I transition between scenes.

Hi all. In Level 1 (or any other game level) i use “Esc” for Pause Menu. From Pause can go to the Main Menu (Main Menu – is another scene inside which has Shop, Authors etc.), or in the Level Menu, which is also another scene. How do I get back to the game level? Not in the beginning of the game level, and in the place where you paused it? Need some sort of system to save the game? Or what? Thank you.