Fit every screen sizes

Hello everyone, I just finished an endless runner game and i tested it on different android devices. The problem is when i run it, the scene doesnt fit the screen.,the camera is following the player and the scene is moving but i can only see half of the whole scene. When i tested it on bluestack,i can see 75% of total screen of my original game + the scene goes black sometimes. What is the best way so that i can fit the whole scene of the game to every screen sizes? The camera I used is orthographic.

Thanks @Sergio7888 for the reply. I have already used the methods you have mentioned. What i was asking was to fit all the aspect ratio automatically. If i choose one resolution from the drop down menu of free aspect it will only work for devices whose resolution i had chosen. So for the code part I got the code here >>> mobile - How do you handle aspect ratio differences with Unity 2D? - Game Development Stack Exchange and it is working fine on different resolution.

@Dream_in_code

Hi there, the same for me. After looking around on the internet about 2 hours :(.
Watching a lot of tutorials video. Finally I found the full tutorial that solve this issue.
Tested and it worked for me.

Link: [SOLVED] Full tutorial: Build 2D game fit to any device screen size, resolution in Unity 2018 - YouTube