SO YOU THINK YOU CAN...?= This is a common ironic expression that in fact means "I don't think you can...".

TELL HEAVEN FROM HELL= Know the difference between right and wrong. The expression TELL -A- FROM -B- means: know the difference, distinguish.
- I can't tell a male cat from a female cat, they look exactly the same to me.
- Kevin is really stupid, he can't tell a television from a poster on the wall.

BLUE SKIES FROM PAIN= The complete sentence would be "so you think you can tell blue skies from pain?". Again, I think you don't know the difference between a nice feeling or situation (blue skies) and a bad feeling or situation (pain). So you are not prepared to distinguished between what's good and what's bad, you're completely lost.

CAN YOU TELL...= Again, we have the same expression but in a different form: CAN YOU TELL -A- FROM -B-?, which means, "do you know the difference between -a- and -be-?

A GREEN FIELD= A piece of cultivated land covered with grass.

STEEL= A metal which is an alloy of iron and carbon, very hard, cold and stainless (it never rusts).

RAIL= A structure made of bars forming a barrier or guard; a railing. (see picture)

A green field is a nice thing, full of life, a steel rail is a dead thing, cold and artificial.

VEIL= A piece of light fabric hung to separate or conceal what is behind it; a curtain. Sometimes used by women to cover their heads, and in Islamic countries, maybe their faces too.

A smile is something nice that opens your heart to other people. A veil is something to conceal, to cover, to separate.

DID THEY GET YOU TO...= If someone gets you to do something, they convince you, force you or deceive you to do something.

TRADE= Exchange.

GHOSTS= The spirits of dead people that appear back in this world.

ASHES= The grey or black dust or powder that remains after something completely burnt.

COOL= Cold.

BREEZE= Light wind.

COMFORT= /kʌmfə*t/

WALK-ON PART= A minor role in a theatrical production, usually without speaking lines. So to play "a walk-on part in the war" means to be in a war but without doing anything really important.

LEAD-ROLE= A major role in a theatrical production (or any other place). To play the lead role is to be the most important person, the leader, the star.

CAGE= A small place completely closed with bars, usually to keep animals inside, like birds in a house or animals at the zoo.

I WISH YOU WERE HERE= I miss you; I want you to be with me. We use the expression I WISH (+ past) to express a desire, something we really want.
The verb WISH (desire) is followed by the past subjunctive. The subjunctive form of English verbs have almost disappeared, and now there is no difference between the simple past and the past subjunctive, but with the verb "to be" we can still make the difference, though that's disappearing too.
To be, simple past: I was, You were, He was, We were...
To be, past subjunctive: I were, You were, He were, We were...
- I wish I were rich (more correct) = I wish I was rich (getting more common)
With other verbs there's no subjunctive form, so we simply use the simple past after the verb WISH:
- I wish I had more friends.
- I wish you loved me.

FISH BOWL= A container made of glass with one or more fishes inside.

YEAR AFTER YEAR= Every year, all the years, without end.
We can also say "day after day", "time after time", etc. to express the same idea (always the same, never changing).

THE SAME OLD GROUND= Here we use OLD to express that it doesn't change, it's always the same. The sentence "running over the same old ground" means "doing always the same things", "our life doesn't change".