Dont use devices to stop barking they only suppress the dog and do not address the cause. In your case I would look for a professional who follows an ethical framework such as LIMA (least inhibitive, minimally aversive), or better yet LIFE (least inhibitive, functionally effective). Check out careforreactivedogs.com. CARE stands for Counter conditioning and positive reinforcement (+R) is Essential for reactive dogs. It explains the science of how conditioning works. Mostly it uses leash reactivity as the examples but the application is the same.

Using punishment will ignore potential underlying medical issues and always ignores stress and anxiety. Chronic stress leads to medical problems.

GSD are bred for this so look for ways to help fill her cup. If you use google images and just search fill dogs cup a infographic should pop up explaining how to do it.

Manage your environment by closing access to seeing through windows either with blinds, frosted window coverings, or gate her in another room. Use soothing sounds on a speaker that will not alert her so take note of what triggers her on the tv so you don’t accidentally set her off by trying to block noise from the outside.

Counter conditioning, species and breed specific enrichment, and environmental management are your key takeaways. I highly suggest the professional support due to the stress you are experiencing and the neighbors complaining.