Stav, at 15 probably the last thing you want to hear is some stuffy advice like "planning ahead", "analysing" etc.. etc..
But seeing as you asked for comments......
Is this an image of your attractive young lady friend Sasja, or is it a "cool" background with a random female figure in front?
Seeing as you mentioned the model by name, then we can assume that the subject here is Sasja.
In this case your image should be working to make her look the best she / you can - and not overshadowing her.
So
(Like Arandel and Britsdad pointed out) you should be:
- Retouching the model - ironing out the jeans,enhancing the hair / lips etc....
- Adjusting the background to make her stand out better.
The subject is basically black and white, so a good move with your background would be to go somewhere else - maybe a mid blue instead of the black.
If you extended the light streak behind her to include her hair, you'd have a more dramatic result.
Besides (all

) that, good work!
Rô