If the second screenshot is the low poly retopo only, and the original one is not below it, meaning if those black lines come from just one mesh, the same retopo mesh, then yes, that seems to be a problem. I saw it and thought it’s just the original poking through the low poly. That might be you have extra edges floating or duplicated vertices. Maybe a good old merge by distance could solve it.
Also with the retopo you are trying to get the defining features of the object, a silhouette of sorts, since all the detail is going to come from the bake, assuming that is what you’re going for, like in Chunck’s course. So the retopo’ed object is not going to look super the same.
You know, Kent goes through this workflow in the super mega course of the Collabs, the one with the Spice Vendor House:
https://cgcookie.com/playlists/156-collab-02-2021
