To successfully install and work with the asset without bugs, we advise you to follow a few simple steps:
Download and install Unity 2020.3.25.
Create new project and import Bullet Master 3D asset.
Then import Text Mesh Pro and download and import NavMeshComponents.
After that asset almost installed. Open Build Settings and check that all scenes are added to Scenes In Build. It should be like the picture.
5. If the scenes are not listed, you should add them manually. To do this, open the scenes in order and click Add Open Scenes.
6. After you have completed all these steps, you can start the game by starting the Main scene.
We hope you succeeded, but if you encounter any problems when installing the asset, you can ask your question here.