Is turning off engines before landing "Normal"? I was traveling by Airbus A380 recently and I was sitting near the wing.
Throughout the flight, I could hear the airplane noise even with headphones on.

Suddenly before landing, everything went silent. There was no noise at all.  There was a strange silence throughout the aircraft.  Everyone was scared and looking at each other, some even started praying.

But we landed perfectly fine. It was like routine landing.

So, I want to ask, whether it was normal? Or the pilot avoided telling us something went wrong? 

P.S. Before starting the landing process, the pilot informed about the weather being fine and said "there's a safety manual in your seat pocket."
There's virtually no chance of the pilot deliberately switching off all 4 engines, and even less chance of all 4 engines failing at the same time. It's not entirely impossible for it to happen, but it definitely wouldn't be quietly ignored within the aviation community. I promise you that you would've heard about it afterwards.

That said, the A380's engines are modern, quiet, and actually mounted quite a long way out on the wings, this makes them fairly quiet when idling, even when compared to other aircraft. This is particularly noticeable after a long flight where they've been running at fairly high power for 8 or more hours, and is even more the case if you're not used to the A380, eg if you usually fly on common twins such as the A320, 737, 777 which are much louder within the cabin.

I suspect, but can't be sure, that the engines were simply pulled back to idle (minimum power/thrust) and it sounded much quieter than you expected.

But no, the engines were almost certainly not simply turned off, that just doesn't happen. The only thing I can think of that would cause that would be a flame-out, and you'd definitely notice that!