*Final Revision?*
 
Segðu mer þat, Freyr,
Tell me, Frey,
 
folkvaldi goða,
thou ruler of the Gods,

 
ok ek vilja vita:
I want to know,

Hvi þú einn sitr
why do you sit  alone 
 
endlanga sali,
in the endlong halls
 
minn dróttinn, um daga?
my      lord,    during the-day.

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Tell me, Frey, captain of the gods,
I want to know,
Why do you my lord, sit alone in the empty, echoeing halls day after day?
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*notes*
valdi=ruler
ok is silent, used for flow and emphasis
Hvi þú - Why do you
einn-one, or alone
eindilangr=along the whole extent of, from  one end to the other,
ok lagðist þar endilangr, at full length.
um = during, in the course 
´day after day´is how Vigfusson translates um daga in the context of the verse.
 
 
" the "end-long" hall is simply a BIG/EXTENDED hall, which accentuates the lord's sadness
as he sits there alone. Not forgetting that this is poetry, the implication is almost "alone in the empty, echoing
halls". " (E)
"Freyr "staring at" [the [empty] walls] of his halls "all day". (=image of desolation))"  (K)
 
Thanks to all who have provided corrections/improvements. I hope you do not mind if I post your quotes in revised translations as an elucidation of context and meaning.