Question 3D player goes through walls

Hello there.

I recently have this problem. So basically the player (3D cube) goes through the walls which is a boundary. That is not what I want. I want the player to stay within the walls no matter what. I applied a box collider to the walls including the floor. I suspect the other cubes interfere with the player with force. Please refer to the video below. Any help / tip relating to this issue will help a ton. Thanks!

Objects
- Player Property (Box collider : is trigger = true)
- Walls including floor Property (Box collider : is trigger = false)

Video
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Hi,

Have you watched this playlist of tutorials?
https://www.youtube.com/playlist?list=PLX2vGYjWbI0TiP080ELGDurOmz5NAg5CI