Default workspace is empty after build

I’m not able to see the folders in workspace, showing empty in pipeline job, adding the piece of pre-written code below:

            echo $JVM_version
            echo s-$brand_name-HD-PVR_Lite-tsc-k1p-sat-halv$HAL_version-jvm$JVM_version
            cd $Build_Dir
            echo deleting $Local_Dir folder
            rm -rf $Local_Dir
            echo $Local_Dir folder deleted succesfully.
            mkdir $Local_Dir
            chmod 777 $Local_Dir
            cd $Local_Dir
            git clone "URL"
            other activities

When I’m giving the location of default workspace in Build_dir, then I’m able to see files and folders in workspace as well but build files are also there so that will create confusion, So workspaceDir and Build_Dir should be different,
is there some problem with above code? why default workspace is empty?

Not clear where your problem is. How and where is Build_dir and all the other variables defined? You use single quotes in your sh step which means variables are not extrapolated by Jenkins but only by the shell. So Build_dir would need to be an environment variable.
It helps when you show your complete pipeline and the log output (redact sensitive information)