Here’s my translation

Alan

Karlar váru at skinnleik margir, heimamenn Markúss. 
Many men were at a ‘skin-game‘ (dat sg), the-members-of-the-household (<heimamaðr>, Z1 - from context, ie see next sentence, not just the servants) of Markús.

Loftr, sonr hans, var sjúkr, ok var hann því eigi at leiknum. 
Loptr, his son, was sick, and he was therefore not at the-game (dat sg).

Þeir Gísli ok Magnús váru börn at aldri.
They, Gísli and Magnús were (still) children in age.

Nú er Markús heyrir sagt, at þeir Ingi fara þar um tún, þá tók hann öxi í hönd sér ok gekk út á hlaðit í móti þeim ok hjó þegar til Inga, ok kom höggit framan í enni honum, og varð þat sár ekki mikit, því at Ingi hjó í móti til Markúss ok hjó í sundr viðbeinat ok þar á hol, ok litlu síðar dó Markús. 
Now when Markús hears [it] said, that they, Ingi [and co] go there across [the] home-meadow, then he took an axe in his hand and walked out on the-pavement-in-front-of-[his]-homestead in-a-meeting with (ie to meet, confront) them, and hewed at-once at Ingi, and the-blow came into the front of his forehead, and that became (ie was) not a great wound, because Ingi hewed in-return at Markús and hewed a-sunder the collar-bone and [hewed] a hollow there-in, and a little later Markús died.

Ok er hann var fallinn, þá kómu húskarlar hans út. 
And when he was (had) fallen, then his manservants came out.

Maðr hét Sigurðr Þórðarson, ok var hann húskarl Markúss, ok er hann sá hann veginn, þá hjó hann til förunauts Inga, þess er Ketill hét. 
[There] was a person (man) called Sigurðr son-of-Þórðr, and he was a manservant of (the late) Markús, and when he saw him slain, then he hewed at a companion of Ingi, that-one who was-called Ketill.

Hann fell við höggit ok dó þegar. 
He (Ketill) fell with the-blow and died at-once.

Ok er Ketill var veginn, þá hjó Sigurðr þegar til Guðlaugs ok veitti honum sár mikit. 
And when Ketill was slain, then Sigurðr hewed at-once at Guðlaugr, and gave him a great wound.

Þá var Sigurði haldit. 
Then Sigurðr was restrained (lit: [it] was held for Sigurðr ).

Var þá sögð Lofti tíðendin, þar sem hann lá sjúkr, at faðir hans var veginn. 
The-tidings were then said to Loptr, there where he lay sick, that his father was slain.

Þá reis hann upp þegar ok tók spjót í hönd sér ok gekk út, ok lagði til Guðlaugs ok veitti honum sár mikit, ok var Loftr þá tekinn ok haldinn. 
Then he rose up at-once and took a spear in his hand and walked out, and thrust at Guðlaugr and gave him a great wound (his second), and Loptr was then taken and held.

Maðr hét Bárðr. 
[There] was a person (man) called Bárðr

Hann var sonr Ingólfs Bárðarsonar ins svarta. 
He was [the] son of Ingólfr, son-of-Bárðr the black.

Hann var vinr Markúss ok frændi, sviðr maðr ok góðgjarn. 
He was a friend of (the late) Markús and a kinsman, a wise (<sviðr>= <svinnr>, Z2) person and benevolent.

Hann beiddi Loft griða fyrir hönd þeira Guðlaugs ok Inga, sagði þá báða sára, kvað þá til einskis vera at vinna á þeim, en förunautr þeira einn veginn, kvað annat vera hjálpvænligt Markúsi, föður hans, en þá væri fleiri menn vegnir at sinni. 
He asked Loptr for a truce on behalf of them, Guðlaugr and Ingi, said them (ie that they were) both wounded, declared then [it] to be pointless (‘in vain’ ?) to do them bodily injury (<vinna á e-m>, Z12), but (and) their companion, in-the-one (ie same) way (<vegr>, Z3), declared next, [it] to be likely-to-help Márkús, his (Loptr’s) father, but (and) then [there] were more (than enough?) persons (men) slain for-the-present.

Ok af þessum orðum Bárðar váru grið sett meðal manna, ok síðan fór Ingi ok hans félagar í brott. 
And on-account-of these words of Bárðr a truce (gram plural) was made (lit: set) between [the] people (men), and after-than Ingi and his mates journeyed away.

Þessir atburðir urðu tveim nóttum eftir allraheilagramessu. 
These events happened two nights after Allhallow-mass.

Svá bar ártíð Markúss ok Ketils. 
So happens (falls) the-anniversary-of-the-deaths of Markús and Ketill

SÍðan var lýst vígi Markúss. 
After-that was proclaimed [the] slaying of Markús.

Árni Surtsson, förunautr Inga, lét sem hann skyldi óhelga Markús.
Árni Surtr’s-son, companion of Ingi, made as if he should proclaim Markús to be outlawed.