[Chern]

first off- welcome to the sport! I can understand your frustration but you’ll outgrow your fist board soon enough. You’re learning to ride and you’re also learning “buyer beware”. it sucks, but look at it this way, you’re less likely next time. The board will work for what you need it do until your ready for your next board. Put some stickers over the repairs for now so people don’t think your the noob who fixed the board like a 2 year old.
As for the shape of your board, its normal. It’s called reverse camber or rocker profile. Boards with thia shape are fine for a beginner snowboards. As you progress you will pick a different profile shape for your style of riding.
You can read all about all the different profiles.

Understanding the Different Snowboard Camber Types | Snowboarding Profiles

Learn about the different snowboard camber types and what riding styles and abilities each type are most suited to.

snowboardingprofiles.com

 

[Chern]

Those updated photos they help but pictures only go so far on the forum.
For sure take It to a shop and get their professional opinion.
Just make sure you’re not throwing more money at a problem In the hopes of righting a wrong.
If the local shop can repair it for less than the Shipping and restocking fees It might be worth it.
otherwise send it back and move on.
can you even return it?