That's completely normal and happens to almost all laptop screens, especially ones with IPS or TN panels. These panels have limited viewing angles, so when you move to the sides or change the angle, the image darkens and colors get distorted because pixels lose their optimal color outside the front viewing range. If you want to check it out, try slowly tilting the screen to the sides while looking at a clear image and you'll see how it gradually changes. For your everyday use it's not a problem unless you work with critical color (professional photo or video editing), in which case you'd need a better panel like OLED, but for normal stuff it's just an annoying feature of cheap laptops.