i cant build my android game .

You need to fill out the bundle identifier in File>BuildSettings>PlayerSettings>Other Settings>Identification.

The field will display something like “com.examplecompany.examplename”

For this, you fill out the parts as required: com.PutYourCompanyNameHere.YourAppNameHere

For example, if you company is called GameCompany, and your app is called NewGame, then you put this: com.GameCompany.NewGame

Hope it helps.