Can I take 41 MP photos with Nokia 808 PureView?

No, you can’t. Depending on the selected aspect ratio, the full resolution photos are either 34 or 38 MP.

The camera has a super-high-resolution sensor, where the active area is 7728 x 5368 pixels, which totals to over 41 MP. Depending on the aspect ratio you choose, it will use 7728 x 4354 pixels for 16:9 photos and videos, or 7152 x 5368 pixels for 4:3 photos and videos.