Here’s my translation

Alan

3. kafli - Hrani hefndi Vakrs ok vó Sigfús
Chapter 3 – Hrani avenged Vakr and slew (past tense of vega, Z7) Sigfúss

Þat var eitt haust, at menn skyldu leita geldfjár síns til fjalla.
That was one autumn, that persons (men) should (ie had to) search for their gelded-sheep on (the) mountains (plural).

Vakr hét einn sauðamaðr Helga, er í fjárleit fór ásamt öðrum.
A certain shepherd of Helgi’s was called Vakr, who went in (the) search (leit)-for-sheep together with others.

Hrani fór líka. Þeir áttu fjallgöngur saman við Mývetninga. Þá bjó Gauti á Gautlandi.
Hrani went also. They had (kept, held, eiga, Z5) (the) mountain-courses (ways, plural) together with (the) Mývatn (Midge-Lake)-folk. Then (ie at that time) Gauti lived at Gautland.

Hjá honum var þá maðr, er Sigfúss hét, mesta illmenni ok sýndi mörgum ójöfnuð sinn.
Near him was then a person (man), who was-called Sigfúss, the greatest man-of-evil (cruelty) and (who) showed to many (people) his unfairness.

Hann fór ok í fjárleit með Mývetningum.
He went also in (the) search-for-sheep with the Mývatn-folk.

Svo bar til, at þeir hittust, Vakr ok Sigfúss, ok gengu saman um hríð,
(It) so happened that they, Vakr and Sigfúss, met-each-other, and (they) walked together for a while.,

þar til þeir hittu sauðahóp ok eltu hann lengi dags, unz þeir kómu at gjá einni.
until they hit-upon a flock (hópr)-of-sheep and ran-after (elta, Z2) it for a great part of the day (cf lengi vetrar, under lengi), until they came to a certain chasm (rift, dual senses intended, I wonder?).

Þar náðu þeir sauðunum ok könnuðu þá. Átti Helgi krókr sauðina.
There they got-hold-of the-sheep and reviewed (ie mustered and identified, kanna, Z1) them. Helgi ‘Hook’ owned the-sheep.

Meðal annarra var þar einn sauðr öðrum stærri, er Vakr átti sjálfr.
Among the others was there a certain sheep, larger than (the) others, which Vakr himself owned.

Sigfúss falar sauðinn ok kveðst jafnvel vilja hafa hann fyrir ómak sitt.
Sigfúss demanded (for purchase) the-sheep and declared-of-himself equally-well to want to have it (ie the sheep, sauðr is masc) for his trouble (in participating in the search?).

Vakr færðist undan ok vildi eigi láta sauðinn.
Vakr conveyed-himself away (showed his disinclination?) and wanted not to give-up (láta, Z2) the-sheep.

Kífuðu þeir nú um þetta, þar til Sigfúss hefr upp öxi sína ok höggr til Vakrs, svo í heila stóð.
They quarrelled now about this, until Sigfúss raises up his axe and hews at Vakr, so (it, ie the axe) stood (lodged) in (the) brain.

Í því kom Hrani ok förunautar hans ok sjá, hvat um var, at Vakr er veginn.
In that (instant) Hrani came and his travelling-companions and (they) see (present tense), what was about (ie what the upshot was), that Vakr was slain.

Spyrr nú Hrani Sigfús, hverju þetta sæti, en Sigfúss segir slíkt er var af viðskiptum þeirra.
Hrani now asks Sigfúss, to what this amounts (sæta, Z4?), but (and) Sigfúss says such as was of their dealings (quarrel).

Hrani mælti: "Víða kemr fram ójöfnuðr þinn ok illmennska, ok vil ek nú hefna hans á þér."
Hrani spoke: ‘Your unfairness (nominative, subject) comes forth (ie appears) far-and-wide (extensively) and (your) wickedness (cruelty), and I want now to avenge him on you.”

Sigfúss mælti: "Eigi mælist ek þá undan þér," ok hleypr at Hrana ok höggr til hans með öxinni, en hann brá skildi fyrir sik.
Sigfúss spoke: “I do not decline (lit:speak-myself-away from) you,” and leaps at Hrani and hews towards him with the-axe, but he (Hrani) quickly-drew (his) shield in front of himself.

Kom þá höggit utan á hnét ok renndi út af. Varð þat allstórt sár.
The-blow came then from-without onto the-knee (kne, m) or nuts! (hnot, f) (both unlikely but I can’t find anything better, clasp?) and ran out from (it). That became (ie was) a very-large wound,

Nú höggr Hrani aftr til Sigfúsar saxinu Helganaut. Kom þat högg á handlegginn ok nam brott öxlina við síðuna,
Now Hrani hew back towards Sigfúss with the short-single-edged-sword Helganautr (Helgi´s-gift). That blow came onto the arm and took away the-shoulder along-with the flank (side),

ok féll hann at vonum dauðr niðr.
and he fell down dead according-to-expectations (ie as expected, ván).

Varð nú mikill krytr um þetta milli Mývetninga ok Hrana. Heygðu þeir þar Sigfús.
(There) became (ie was) now a great hubbub about this between (the) Mývatn-folk and Hrani. They buried (in a how) Sigfúss there.

Ok eftir þetta sneru menn til byggða með fé sitt, er fundit höfðu.
And after this people (men) turn (ie go) to (their) abodes with their-sheep, which (they) had found.