Why are blocks in Minecraft black on one side?

Some of my blocks are black and that only works if I build blocks. What is the problem and how do I fix it?

That's the shadow or not?

No, that does not look like shadows, it's only on one side and only on certain blocks or points. Or do I have to update the video driver of my PC?

I think that's just a bug, I had when playing Minecraft, too.

Have you ever tried to reinstall the game?