Hi vanhelsing and welcome to the forum...
1). straighten the horizon, but then the model would probably be crooked (?), background is too cluttered with people, and the "growly" clouds detract from the main subject, your model...so this is just a snapshot - also, , if she is going to look to the left, then I would have put the model on the right side of the image, looking into the "negative space" on the left.
2). this one does nothing for me, would have preferred to see the model's face...for me, just a snapshot...
3). all the "greenery" is distracting...and there is no emotion from the model...dark blue sky tends to let your eye wander out of the picture and is distracting...plus that "blue thing" that is sticking up in the left-centre part of the picture is also a bit distracting.
4). Very nice, the model is smiling and the background is nicely OOF so as to not be distracting.
5). best one of the bunch (#4 is a close second)...both models are smiling and they are obviously looking at something off camera - but this image also conveys a sense of emotion, in my opinion, the models are having fun...and they are more to the right side of the image looking to the left, better composition than the first one.
Nice start if you are going to shoot models and people, but
watch your backgrounds... they should not detract from the main subject of your image, unless, perhaps, if you were doing nature, wildlife and landscapes, then the background can be a very integral part of the image.
You might want to look up some stuff on composition on the web, for example ...
Basic Photography Techniques - Photographic Composition, Center of interest, Subject placement, Simplicity, Viewpoint and camera angle, Balance.
My 0.02¢ FWIW.
Cheers,
WesternGuy