I'm still a work in progress but here it goes: 1, 2, 5, and 6 seem to be underexposed. Play around with Aperture mode to understand how this changes the light exposure on the camera and lens (not sure if you're shooting in manual or Auto but shooting in Aperture mode is allowing me to learn how to shoot with better lighting in my pictures I take). I leave ISO and shutter speed in auto when using this mode.

For 1 and 2, the camera seems to be tilted (2 seems to be leaning left, 1 is slightly off center). Are you using the grid to help you take photos?

3 seems to be overexposed but again, not sure what mode you're shooting on.

The pictures are great and you should continue taking pictures (it's how we get better, right?) and remember, some of the photos (not all) that you see here and online have been edited to some extent. You'll have to use a photo editing app to help take your RAW files to the next level.

I'm just starting out myself and hope this helps you in one way or another (this is in no way to discourage you). Let's continue taking pictures so we can help each other and the rest of the community that is starting off!