Have you heard of the ~아/어/etc. 다가 form before? This form is not the same as the regular ~다가 form, nor is it the ~다가는 form I taught previously. It's also not ~에다가, which can attach to nouns. And finally it's not the same as ~ㅆ다가 which I also explain in this live stream.
~아/어/etc. 다가 is an advanced level grammar form that's used to show that two actions happen in order, that both actions happen in different locations, and that an object is moved from one location to the next one.