*Full 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 long hall
 
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 longhall 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.