How can we know what dogs are saying
It is hard to tell what a dog is saying unless you have spent a lot of time with it. It whines when it wants to go out, and have different bark types when it needs something. You can ask a dog instructor to interpret some moves.
I heard before that the "Growl-then-bark" means stay away to a possible intruder,etc.; "Bark-then-growl" indicates the dog is afraid, wary, etc. (Tail wagging, of course, is a good thing.)
Well you need to know them well. Once you do, it'll seem like they're actually talking!!!
Body language and tone are universal throughout the animal kingdom, including humans
Body language or get someone professional, read up on it
You can tell based on their movements, placement of ears, barking, whining, looks, etc. The better you get to know a dog the better you will understand it.
Well I know how they talk they bark dahhhhhhh
By their acions
ikr its hard but by their body language you will be fine