Problem with UV MAP and Unwrap I Created a low poly barrel with three cylinders. The first one I created is  the barrel shape, the other two are the rings around the barrel.

I have one problem with the UV MAP (Blender 2.82), when I select all vertices, Blender automatically creates streched a UV Map with 2 circles and 16 faces. I don't want this UV Map but I can't delete it.

I marked the barrel top, barrel bottom and all edges from one side with "Mark Seam" and after this I unwrapped my model. Unwrap creates something like 2 UV Maps in one, one over other, the first with 2 circles and 16 faces stretched and the second correct but I can't delete the first one. 

How can I solve this?
Pressing u and clicking unwrap should give you your new mesh with the seams that you have defined. You don't need to "delete" that one.