Help needed with funny black lines in 3ds Max 16



First time posting here and I am hoping someone could help me with my 3d modeling. I have not done any modeling in 4 years and I’ve finally decided to start getting back into it. I am using 3ds Max 2016 and as you can see from the images, I have black lines appearing in my polygons.

My modeling is very basic, I started by creating the outline with splines - lines and once I have the shape I need, I converted it to an editable mesh. I have tried a few things to get rid of these black sections, such as flip polygons or adding a Normal modifier but nothing has worked.

Thank you in advance for any help