Assessment context and image originals from this thread: https://www.reddit.com/r/PostureTipsGuide/comments/150i56f/help/
This is a pretty standard pattern repeated many times around here.
Feet in wrong position. The blue lines, outsteps should be parallel to each other.
Knees released, although not too badly.
Pelvis shifted too far forward, iliacs too low, sacrum too high.
That orange line is your belt line and should be horizontal. The 2 white lower arrows show the movement of your pelvis (iliacs and sacrum are both part of it) in relation to your torso. On this side view we could state that you are rotating the pelvis anti clockwise.
The other part of your torso - ribcage or upper torso is performing exactly the opposite rotation. We could say clockwise rotation of your ribcage. Again, as the upper white arrows suggest.
These two rotations of the major objects of your torso (pelvis vs. ribcage) result in the shape of your spine marked with red curve.
The yellow line is your sternum, that is the front of your ribcage and we often use it to identify the slant of the upper torso. These two rotations are habitual movements. You may not be wishing for them, yet they happen.
In order for you to straighten your spine, you would have to make a deliberate decision to make the two parts rotate in reverse. That is rotate the pelvis clockwise and ribcage anticlockwise. Such movements will lead to straightening your spine, lengthening and widening your torso.
Although, if you try to do it, you will probably find it very hard at first. If not impossible.
You are retracting your arms backwards which is what is lifting your shoulders up. Your head seems to be retracted back as well. The head position together with the position of the shoulders is shortening your neck.
The blue spots (ankle, knee, iliac (anterior superior iliac spine), bottom and top sternum should all be on the green plumb line.
All 100% fixable, you just gotta learn how to direct the movements of each part of your body to the desired configuration. You also gotta understand what the desired config is and why is that it's desired.
If you need more input, feel free to ask.