Here’s my translation

Alan

En þenna sama dag reið Atli son Úlfs hins skjálga norðan yfir heiði við tólfta mann. 
And this same day, Atli son of Úlfr the Squinting rode from-the-north over (the) heath with (the) twelfth person (man) (ie with eleven others).

Hann varð var við fundinn og fór til og réð þegar til meðalgöngu og kvaðst þeim veita mundu er að hans orðum vildi gera og þar kom að hann fékk skilið þá því að hvorirtveggju voru mjög sárir. 
He became aware (ie learnt) of the-meeting (battle, confrontation) and journeyed towards (it) and at-once set about (ráða til e-t, Z16) an intercession (lit: a going between) and declared-of-himself (that he) would help those who did according-to his words and (it) came (about, ie transpired) there that he was-able-to separate them because each-of-the-two (sides) (nom plural) were much wounded.

Þar létust fimm menn af Þóri en fimmtán af Steinólfi. 
There five men of Þórir’s died but (and) fifteen of Steinólfr’s.

Þar heitir Grásteinsdæld er þeir börðust upp frá Bæ.
There (ie that place) is-called Grásteinsdoeld (Gray-Stone-Hollow) where they fought up from Boer.

Atli fylgir þeim Steinólfi heim í Bæ og voru bundin sár þeirra. 
Atli accompanies them, Steinólfr (and co) hone to Boer and their wounds were bound (dressed).

Þeir Þórir riðu vestur heim og voru allir sárir og engi maður komst ósár af þeim fundi. 
They Þórir (and co) rode west home and all were wounded and no man made-his-way unwounded from that meeting (battle).

Um daginn eftir fór Steinólfur heim suður til Fagradals og lá lengi í sárum um haustið og greri seint. 
During the-day after Steinólfr journeyed home south to Fagradalr (Fair-Dale) and lay a long time in wounds (ie in a wounded state) during (the) autumn (fall) and healed slowly.

En um veturinn sló í verk og rifnuðu aftur þá er gróin voru og dó hann af þeim sárum. 
But (And) during the-winter (it) struck in pain (verkr not verk) (ie he was seized by pain) and (they, ie the wounds) opened up again, those which were (had) healed, and he died from those wounds.

Þórir hafði og mjög sár orðið og greru hans sár skjótt. 
Þórir had also become (ie been) much wounded (MnI spelling of sárr, adj masc nom sg) and his wound healed quickly.

En eftir þenna fund tók Þórir skapskipti. 
But (And) after this meeting (battle) Þorir took (ie had) a change-of-temperament (became bitter and twisted).

Gerðist hann þá mjög illur viðfangs.
He became then very bad in dealing-with (ie to deal with),

Það haust hurfu kistur þær er hann hafði gera látið að Valshellisgulli og vissi engi síðan hvað af þeim var orðið.
That autumn (fall) those chests which he had caused (láta) to construct (göra) for (ie to hold) (the) Valshellisgulli (Valr’s-Cave-Gold) disappeared and no-one knew after-that what was (had) become of them.

20. kafli
Chapter 20.

Nú er frá því að segja að til hefnda eftir Steinólf var Þorsteinn son hans og þeir feðgar, Sleitu-Björn og Þjóðrekur dótturson Steinólfs. 
Now (one) is to say about that, that set-on (?) vengeances (plural?) for (the death of) Steinólfr was Þorsteinn his son and that father-and-son-combo, Sleitu-Björn and Þjóðrekr son-of-(the)-daughter (ie grandson) of Steinólfr.

Atli Úlfsson leitaði um sætt með þeim og vildu Saurbæingar ekki sættast ef eigi færu þeir utan er mest höfðu gengið að vígum þeim. 
Atli Úlfr’s-son tried-to-get reconciliation with them and (the) Saurboer-folk wanted not to come-to-terms if they would-not-journey abroad (from Iceland) who had gone (at it?) most (ie the main participants?) as regards to those slayings (plural).

Þórir vildi ekki utan fara. 
Þórir wanted not to journey abroad (from Iceland).

Var Steinólfur bættur fé miklu. 
Steinólfr was compensated-for with much money.

En Guðmundur og Vafspjara-Grímur, Vöflu-Gunnar og Óttar skyldu utan fara og vera brott lengi...
But (And) Guðmundr and Vafspjara-Grímr, Vöflu-Gunnarr and Ottarr should journeyed abroad and be (stay) away a long time.

(Hér vantar eitt blað í handritið.)
(Here is-missing one leaf (page) in the-hand-writing (manuscript).)

... gátu eigi fylgt honum o... er hann sá bardagann hamaðist hann. 
…not able to accompany him…when he saw the-battle he raged (went beserk).

En er hann kom ofan á fjöruna þá féll Steinn niður ... vörðust af skipinu.
But (And) when he came down to the-fore-shore (sg), then Steinn fell down (in battle)…defended-themselves from the-ship.