How to delete black lines inside pen-tool shape ?

Hey guys I m quite a beginnner and actually no matter how hard I try I cannot find any answer to this online.

This is the problem I came across:

Premise: I created this path:

Question: How can I remove those four black lines without compromising anything else ?

What I tried: Deleteing the lines and then rejoining the paths ( rejoining throws errors).

                    Using the shape builder tool. (just shows a black crossed circle instead of the tool)