We're the ones with the opposable thumbs and huge cortex, so IMO we should be learning their language in order to communicate more effectively. Yet, we humans often misinterpret what dogs are really saying - not easy to translate a foreign "language" when it happens at the speed of light sometimes. This lady is a service dog trainer and, if you meet her, you realize that she is an older woman, too heavy and not agile enough to muscle dogs around. One of her videos that I have shows her teaching from a chair. But, she is extremely knowledgeable, has great timing, and I recommend this book to anyone who wants a more detailed knowledge about dog behavior and language...
"Canine Behavior: A Photo Illustrated Handbook" by Barbara Handelman