You have to play around with your exposure (shutter speed). Shoot in M mode, at least f11 for sharpness throughout. Start with the the slow shutter speed that gives optimal exposure to your BG and increase the shutter speed from there till you get a few images ranging from a light to dark. You should have at least 10-12 images depending.
In PP, you'll have to layer at least 2 images. Here's a fast step-by-step.
1) Image 1: nicely-lit and sharp bg.
2) Image 2: nicely-exposed merlion (not over/under, just right. But its up to you)
3) Open both in photoshop. Put Image 2 as a layer above Image 1.
4) Erase the background from Image 2, ie. everything
except the merlion. You can use the eraser tool (use a soft brush to go around the merlion) or use a layer mask.
That's about it. Just sharing what I know. You might want to read up on various PP techniques. I'm a noob learning too. Good luck!