I have a few issues backing up my macbook pro

1. I recently upgraded my mb pro. I was using WD 500 GB external drive to backup my old MB. Now when I try to back up my new MB the back up is stuck at "preparing to backup".

2. I deleted some old backups because the backup drive was getting full. Now those deleted files stay in trash. I can never empty the trash.

Is there any way to fix these two problems? Experts please help.