I can see several things you could do, based on the previous answer & comments, as well as the original question. [Some are repeats.]

1. You need more light.
   Longer exposure if you have a tripod or higher ISO if you don't.
   As your subject is static, you can go really long on exposure. Get a wired remote [10 bucks on eBay] & set the camera to 1s Exposure Delay Mode, to minimise shake.
   If you can't afford a good tripod, put the camera on a table.

2. Stand back further & zoom to fill the frame.
   This will lessen the curved appearance.
   If you're struggling for space behind you, consider moving the display around until you can stand in the hallway & shoot in through the door. No-one has a home studio big enough for photography - so get inventive ;)

3. Try the soft-lights behind you, over your shoulders or just off to your sides.
   This will reduce the overall lighting level [see 1.] but ought to even it out a lot.
   [If you're in the hall, put them just inside the door instead]

4. Am I seeing a bar through the bottom of the sheet? Get a heavier bar.
   To even out the vertical creases the heavier pull will generate, peg out the top & bottom edges on the bar.

5. Most important for product presentation...
   Iron it before you hang it.
   ...or steam it, or water spray it & let it dry in situ.

Late edit
I ran it through Photoshop [very quickly]
This is what you can easily do in post-process. My guess at the colour & contrast are just that - a guess. I've never seen the original to work to.

Remove the barrel distortion, then Perspective crop [next time make sure you're exactly square to the centre of the sheet]
Some lightening & rebalance to make it appear to be white, at least in the centre.
I didn't go for 'digital white', or you wouldn't still be able to see it's a piece of fabric.
I'm trying to decide whether it is actually blue at the edges or if that's variation on the lighting.

What's left really, is the work you need to do before hanging it.
Iron it & make sure it has no grubby marks in the middle.