@Juno:
I do not know if the creator made any of the assets used on this map. But it seems that everything you see is an asset from the workshop. By loading the map in the app (via workshop) you'll be asked to download the according assets. (in this case ~600MB data)
And well, that's actually a very good starting point if you're planning to do something similar.

Did you upload your own textures to make this. where did you get the resources/assets? would love to make my own modern/urban maps

Yes! i've been looking for a map exactly like this!

Hey fella. - I suspect you might work on more maps like that?
This looks simply good, an absolute must-have. Nicely done!