AutoCAD uses a completely different approach to drawing objects than CorelDRAW. Everything is basically rendered as line segments rather than a bunch of closed paths.
For example, to draw a brick wall AutoCAD will make the "texture" as a bunch of 2 point open line segments. In CorelDRAW you would create a bunch of closed rectangles organized into a repeating pattern.
With projects that need a high degree of precision, I'll lock down imported AutoCAD artwork on one layer (after getting it sized to the right scale) and then draw new, clean, closed paths over the top of it. I often do this when reproducing building elevations.
A quick and dirty approach: take the artwork into Adobe Illustrator. Give the open path lines a certain amount of stroke width. Enough that all the gaps between open paths are filled. You have a few options to choose at this point. You can expand all those line strokes, weld them together then break them apart to individually color the resulting closed path objects. Or you can use smart fill tools to create new objects. CorelDRAW has some of the same capability, but seems a little more crash-prone when doing stuff like this.