Here’s my translation

Alan

79. kafli - Af Bolla Bollasyni
Chapter 79 – Of Bolli Bolli’s-son

Í þann tíma er Bolli Bollason bjó í Tungu og nú var áður frá sagt þá bjó
At that (ie the same) time that Bolli Bolli‘s-son lived in Tunga (Tongue) and now was before spoken about, then lived

norður í Skagafirði á Miklabæ Arnór kerlingarnef son Bjarnar Þórðarsonar frá Höfða.
north in Skagafjörðr at Miklabær (Large-Farm) Arnórr old-woman´s (crone’s)-nose (nominative, the subject of this clause) son of Björn Þórðr’s-son from Höfði.

Þórður hét maður er bjó á Marbæli. Guðrún hét kona hans. Þau voru vel að sér
(There) was a man (person) called Þórðr who lived at Marbæli. His wife was-called Guðrún. They (man and wife) were well of themselves (ie well-to-do?)

og höfðu gnótt fjár. Son þeirra hét Ólafur og var hann ungur að aldri og
and had plenty of cattle (or property?). Their son was-called Ólafr and he was young in age and

allra manna efnilegastur. Guðrún kona Þórðar var náskyld Bolla Bollasyni.
of all men (persons) most-promising. Guðrún wife of Þórðr was closely-related to Bolli Bolli´S-son.

Var hún systrungur hans. Ólafur son þeirra Þórðar var heitinn eftir Ólafi pá í Hjarðarholti.
She was his mother’s-sister’s-daughter (ie female cousin). Their Þórðr (and Guðrún’s) son Ólafr was named after Ólafr Peacock (pá not þá) in Hjarðarholt (Herd-wood)

Þórður og Þorvaldur Hjaltasynir bjuggu að Hofi í Hjaltadal. Þeir voru höfðingjar miklir.
Þórðr and Þorvaldr Hjalti’s-sons lived at Hof (Temple) in Hjaltadalr. They were great chiefs.

Maður hét Þórólfur og var kallaður stertimaður. Hann bjó í Þúfum. Hann var
(There) was a man (person) named Þórólfr and (he) was called stiff-person (man)(Keneva Kunz´s translation suggests Stuck up?). He lived in Þúfur (Mounds). He was

óvinveittur í skapi og æðimaður mikill. Hann átti griðung grán, ólman.
unfriendly (hostile) in temperament and a great person (man)-of-fury. He had a grey bull, savage (takes after his owner it seems).

Þórður af Marbæli var í förum með Arnóri. Þórólfur stærimaður átti frændkonu Arnórs
Þórðr from Marbæli was (ie had been) in (trading-) journeys (voyages) with Arnórr. Þórólfr stiff-man (I think this probably should be stertimaðr) had (in marriage) a kinswoman of Arnórr

en hann var þingmaður Hjaltasona. Hann átti illt við búa sína og
but (and) he was a Thing-man (ie liegeman, supporter) of (the) sons-of-Hjalti. He held badly (ie quarrelled, See eiga, Z5) with his neighbours (búi, Z2) and

lagði það í vanda sinn. Kom það mest til þeirra Marbælinga. Graðungur hans
placed that in his custom (vandi) (ie made a habit of it). That came mostly  to (ie  mainly concerned, affected, see koma, Z4) them (the) Marbæli-folk. His bull

gerði mönnum margt mein þá er hann kom úr afréttum. Meiddi hann fé manna en
did to people (men) much harm when he came out-of (ie left, ie returned home from) (the) common-pastures. He damaged (the) cattle (or property?) of men (people) but

gekk eigi undan grjóti. Hann braut og andvirki og gerði margt illt.
went not away-from stone(s) (ie did not retreat when stones were thrown at him). He broke also haystacks and did much ill.

Þórður af Marbæli hitti Þórólf að máli og bað hann varðveita graðung sinn:
Þórðr from Marbæli met Þórólf in speech (ie obtained speech with him, mál, Z4) and bade him keep-watch of his bull:

"Viljum vér eigi þola honum ofríki."
“We want not to suffer tyranny from him.”

Þórólfur lést eigi mundu sitja að fé sínu. Fer Þórður heim við svo búið.
Þórólfr declared-of-himself (that he) would not tend to (ie sit in watch over) his cattle. Þórðr travels home things being so.

Eigi miklu síðar getur Þórður að líta hvar graðungurinn hefir brotið niður
Not much later Þórðr is able to see where the-bull has broken down

torfstakka hans. Þórður hleypur þá til og hefir spjót í hendi og er boli sér
his turf-stacks (plural). Þórðr runs then towards (the bull) and has a spear in (his) hand and when (the) bull sees

það veður hann jörð svo að upp tekur um klaufir. Þórður leggur til hans svo
that it wades through (the) earth so that (it, the earth) takes up (extends, rises, see taka upp, Z12) around (its) cloven-feet (hooves). Þórðr thrusts towards him so

að hann fellur dauður á jörð. Þórður hitti Þórólf og sagði honum að boli var dauður.
that he falls dead on (the) ground. Þórðr meets Þórólf and said to him that (the) bull was dead.