how to fix these bad faces ?

Hey,

I am having some visual problems with a house model; a few faces look weird when in the sun / light (probably cause of me clumsy subdividing), how to fix this in a model editor? (I use MED and Blender) Here a pic ingame and below in MED:

probably the vertex are split. select all those vertex in that line and press "Merge" button in MED

the Geometry is Wrong,

your setted vertex is linear and thats cutting the Shadow
here is the Right way, the yellow dots (vertex) and the Green are Faces,

Solution is simple, select the whole side of the wall, copy it, delete and past back.

Greets

Thank you all for the explanation and handy tips, it looks good now.
Is it possible to change the settings in Blender so I can see the bad there faces there to? Cause now only Med shows them.