Here’s my translation

Alan

Sigmundr var þá mestr höfðingi í Austfjörðum. 
Sigmundr was then [the] greatest chief in Austfjarðar (East Fjords)

Síðan fór Markús vestur á Rauðasand til bús síns ok bjó þar lengi síðan í góðri virðingu. 
After-that Markús journeyed west to Rauðasandr (Red Sand) to his farm and lived for a long time after-that in high (lit: good) esteem.

Markús var eigi goðorðsmaðr ok var þó með öllu ríkr í heraði sínu. 
Markús was not a man-with-the-dignity-and-authority-of-goði (heathen priest) and-yet (but) nevertheless was wholly (lit: with all) powerful (ríkr, adj nominative) in his district.

Svá lét hann bæ sinn húsa stórkostliga, at hans bær var svá húsaðr sem þeir, er bezt váru húsaðir í Vestfjörðum.
He caused to build his farmstead (replete with various farm buildings, <hus>) in-grand-style so, that his farmstead was built just like those which were [the] best built in Vestfjarðar (West Fjords)

Síðan andaðist Ingibjörg, kona Markúss, ok eftir hennar andlát fór Markús í brott af landi ok lét höggva í Nóregi kirkjuvið góðan. 
After-that Ingibbjörg, wife of Markús, died, and after her death Markús journeyed away from [the] land (ie abroad) and caused to hew good church-timber in Norway.

Hann fór suðr til Róms, ok er hann fór sunnan frá Róm, keypti hann klokkur góðar í Englandi ok hafði þær með sér í Nóreg. 
He journeyed south to Rome, and when he journeyed from [the] south (ie North) from Rome, he bought good bells in England and had (ie brought, <hafa> Z6) them with him to Norway.

Síðan fór hann til Íslands með kirkjuviðinn ok klokkurnar. 
After-that he journeyed to Iceland with the-church-timber and the-bells.

Ok er hann kom út hingat, lét hann gera kirkju göfugliga á Rauðasandi, ok til þeirar kirkju gaf hann klokkurnar ok Óláfsskírn, er hann hafði út haft. 
And when he came out hither (ie to Iceland), he caused to build a church worshipfully (or magnificently, looks like and adverb to me) at Rauðasandr (Red Sand), and to that church he gave the-bells and Ólafr’s-baptism (?), which he had had out.

Sú kirkja var síðan vígð guði almáttkum ok heilagri Máríu dróttningu.
That church was after-that consecrated to Gold Almighty and holy queen Mary.

Eftir andlát Ingibjargar var Markús óglaðr löngum af hugtrega þeim, er hann hafði af hennar andláti.
After [the] death of Ingibjörg Markús was continuously depressed by that grief (singular, weak masc dative), which he had (ie took, received) from her death.

6. Frá deilum Markúss ok Inga.
6. About [the] disputes (plural) of Markús and Ingi.

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

Hann var Magnússon. 
He was Magnús’s son.

Hann bjó í Patreksfirði á þeim bæ, er hét at Hvalskeri. 
He lived in Patreksfjörðr on that farm, which was-called at Hvalsker (Whale-Skerry).

Ingi var mikill maðr vexti ok ljótr, grályndr ok gárfenginn.
Ingi was a large person (man) in-stature and ugly, spiteful and given-to-mocking (nastier than buffoonery).

Á þeim bæ, er Ingi bjó, var bænahús. 
On that farm, where Ingi lived, was a house-of-prayer (chapel).

Þat lá undir þá kirkju, er á Rauðasandi var. 
That belonged to (lit: lay under, <liggja undir e-n>, Z8) that church, which was at Rauðasandr.

En þat var boð ins heilaga Þorláks byskups, at hvergi skyldi bænahús niðr falla, þar sem áðr váru, ok ef bænahús hrörnaði eða felli niðr, þá skyldi af tóftinni gjalda sex aura til graftarkirkju þeirar, er bænahúsit lá undir. 
But (And) that was [the] order of [the] holy bishop Þorlákr, that nowhere( <hvergi>, adv) should a house-of-prayer (chapel) fall down, wherever [they] were already, and if a house-of-prayer (chapel) fell-into-decay (<hrörna>, CV) or fell down, then (one) should pay six aurar (ounces) on-account of the-ruins (<tóft>, MnI dictionary) to that church-with-a-burial-ground (<graptarkirkja>) which the-house-of-prayer (chapel) belonged to (lit: lay under).

Á þeim bæ, er Ingi bjó, fell bænahús ofan, en þat hús lét Ingi eigi upp gera, ok eigi vildi hann gjalda af tóftinni. 
On that farm, where Ingi lived, the house-of-prayer (chapel) fell down, but (and) Ingi did not cause to rebuild that building, and he did not want to pay on-account-of the-ruins (<tóft>, MnI dictionary).

Þat fé heimti Markús at Inga, en hann galt eigi féit. 
Markús claimed (<heimta e-t at e-m>, Z3) that money from Ingi, but he (Ingi) did not pay the-money.

Þaðan af óx óþykkt með þeim Markúsi ok Inga.
From-that time  (<þaðan af>, Z3) a discord (<úþykkt>) grew (<vaxa>) between them, Markús and Ingi.