Spanish language Q&A Forum

I'm almost 2 years into learning Spanish and I get lost after hearing a couple of words if I close my eyes.  I watch shows and listen to Spanish podcast, and my ear for Spanish has not developed at all.  What could I possible do to change this?

Hola, no entiendo estas frases: 

1) justo de lo que se trata, 

2) es de ver que todos somos distintos

Entiendo la idea de la paradoja--que la igualdad es importante pero, al mismo tiempo, somos individuales--pero no puedo traducir las frases. 

Una suposición:

1) in fairness to what we are dealing with

2) one must see that

In the test the question is "Coloca las plantas _____ sol." I understand that "al" is the correct answer as far as a contraction, but why do you use "a" in this instance? Why is it not "en el sol"?

Que tal,

How interchangeable are tras and detrás? Is one preferred over another, and if so, does it vary by country or age or context?

I'm think about basic use meaning 'behind,' such as "El niño se escondía tras (detrás) las cortinas."

Thanks!

How would you write “My leg and knee hurt”? It seems like I could write it “Me duele la pierna y la rodilla”, but not “Me duelen la pierna y la rodilla." Are either of those correct?