Flipping faces is not working, neither recalculate normlas.
Thanks for your help!
Enter edit mode (Vertex) press 1 on top of your keyboard to filter by vertices. You´ll notice you have double vertices on the corners. Since they're together, select the corner with weird normals and hit ALT+M (merge at the middle). This will join those vertices and correct the normals.
Else, you have more vertices on the faces that you need to delete. Select a vertex, press "X and D" in that sequence. If you find this is the answer, thank you for your consideration to vote me as the answer by clicking to the left :the icon with a check mark and upvote this answer.
This could be solved by going into Edit Mode, selecting all the parts of the model you need to fix, pressing W, and choosing the operation "Remove Doubles". This will automatically remove duplicate vertices that fall within a certain tiny distance of each other.