Streighten mesh?

Im new to blender and i have a question: i created an object, but i have faces of the mesh that are like crooked when smoothing… when its flat it looks pretty good, but still wrong when redering, see the picture

how do i streighten these faces?

Tab into Edit Mode. Hit ‘A’ to select all (if they aren’t already). Hit ‘CTRL-N’ to recalculate the normals.

The normals got wonky on your mesh. A normal is a vector that determines the direction to which a polygon/face is pointing. Normally (ha! ha!) they should be consistently pointing to the outside (or inside respectively) of your mesh, but sometimes a polygonal modeller like Blender can get confused about the directions. ‘CTRL-N’ forces Blender to reevaluate the normals’ directions in regard to the rest of the mesh.

This is magic!

Edit mode, select all, W -> remove doubles, make sure all is still selected and Ctrl+N to make normals consistent and pointing outside.

Post the file if that didn’t help. Can do that here, or and share the link

Good point. Sometimes it is screwed geometry that causes the normals to turn the wrong way. ‘Remove Doubles’ will take care of any coplanar geometry in your mesh.