A new created face does not sharing the old one shading information I wish I could have a better topic title for this but I'm just a newbie and I don't know what people call it, so... I'm here with a short video to explain my problem.

Here is the link: https://www.youtube.com/watch?v=0YOBvL1sIig

As you can see I try to edit the old model that I bought from other people. I can do a simple geometry and UV crafting but look like something wrong here.

The new faces I created didn't share the same shading information from the old one, you can simply separate those by looking at the different reflections on the model.

So, I'm begging for any help and thank you for sparing your valuable time with this topic
Select all faces and Recalculate Normals, it looks like the face normals are facing in different directions, recalculate normals should do the trick. All the best Marco