Here´s my translation

Alan

Ok er Hrafn hafði eigi lengi heima verit, þá fór hann í Vatnsfjörð at heimboði Þorvalds ok þá af honum stóðhross góð. 
And when Hrafn had not been long at home, then he journeyed to Vatnsfjörðr at [the] invitation of Þorvaldr and accepted (þá, past tense of þiggja) from him good stud-mares (plural).

Þeir mæltu þá enn af nýju til vinfengis með sér. 
They spoke then yet again of [their wish for] friendship between themselves.

Nökkuru síðar fór Þorvaldr á Eyri at heimboði Hrafns ok þá af honum góðar gjafir, ok var þá vinfengi þeira ít bezta.
Somewhat later Þorvaldr journeyed to Eyrr at [the] invitation of Hrafn and accepted (þá, past tense of þiggja) from him good gifts, and then [ie at that time] their friendship was the best.

12. Frá hvalreka ok frá Víga-Hauki ok Lofti.
12. About a whale-stranding and about Víga-Haukr and Loptr.

Í Selárdal kom reyðarhvalr góðr ok mikill á land þat, er Ragnheiðr átti. 
In Selárdalr came a rorqual good and large onto that land which Ragnheiðr had.

Ok er Þorvaldr frá þat, fór hann í Selárdal ok bað Ragnheiði, at hon skyldi selja honum nökkurar vættir hvals, en Ragneiðr lét hann hafa tólf vættir hvals ok mælti, at hann skyldi gjalda henni jafnmikinn hval síðar, þá er ræki á fjörur hans. 
And when Þorvald was-informed-of that, he journeyed to Selárdalr and asked Ragnheiðr, that she should hand-over to him several ‘vættir’ (several x 80 lbs) of [the] whale, but (and) Ragnheiðr (typo) let him have 12 ‘vættir’ (12 x 80 lbs) of [the] whale and spoke, that he should repay her equally-as-much whale later, when [it] should-be-tossed (stranded) on his beaches (foreshores, plural).

Fyrir þann hval galt Þorvaldr aldri síðan. 
Þorvaldr never repaid for that whale later-on.

Ok er hann fór á brott ór Selárdal með hvalinn, gisti hann í Lokinhömrum, ok er hann var þar um nótt, þá var stolinn í brott sumr hvalrinn. 
And when he journeyed away out-of Selárdalr with the-whale, he passed-the-night in Lokinhamrar (Lokin?-Crags), and while he was there during [the] night, some of the whale was stolen away.

Sá stuldr reyndist á hendr þingmanni Hrafns, þeim er bjó á Sléttanesi. 
That theft was-proven-against a liegeman of Hrafn, that-one (<þeim> is masc dat sg) who lived at Sléttaness (Ness of Flats, ie flat lands)

Ok er Hrafn varð þess varr, varð hann skjótr til ok bauð honum at gjalda fyrir þingmann sinn slíkt fé sem Þorvaldr vildi gert hafa fyrir hvaltökuna. 
And when Hrafn became aware of that, he became (ie was) quick to [action] and offered (<bjóða> not <bíða>) to repay him on-behalf of his liegeman, such money as Þorvaldr wanted to have fixed (as a fine, göra, Z10) for the-whale-taking.

En Þorvaldr vildi eigi þiggja at Hrafni fébætr. 
But Þorvaldr wanted not to accept compensation from Hrafn.

Ok litlu síðar fór Þorvaldr ok rænti þann mann, er tekit hafði hvalinn, ok þaðan af tók Þorvaldr at ganga á hendr þingmönnum Hrafns at öðru hváru. 
And a little later Þorvaldr journeyed and robbed that person (man), who had taken the-whale, and from-that-time Þorvaldr started to go against (ie attack, cause trouble for, see <á hendr>, under <hönd>, Z*) Hrafn’s liegemen according-to-either-the-one-or-the-other (ie chosen pretty much at random, couldn´t find in Z or CV).

* Unless I’m missing something, it seems to me <ganga á hendr e-m> is unlikely to mean <to submit, go into the hands of> in this context.

Maðr hét Haukr, er kallaðr var Víga-Haukr, sonr Orms Fornasonar. 
[There] was a person (man) called Haukr, who was called Víga-Haukr, son of Ormr, son of Forni.

Hann var norðlenzkr at ætt. 
He was from-the-North (of Iceland) by extraction.

Hann kvángaðist vestr á Rauðasand ok fekk Hallberu, dóttur Markúss Gíslasonar, ok fór þangat vistfari til Lofts. 
He took-a-wife west at Rauðasandr and got [in marriage) Hallbera, daughter of Markús, son-of-Gísli, and changed-his-abode (presumably = <vista-fari>, CV, lit: went on an abode-passage) to Loptr’s-[place].

Þá er Gísli Markússon var fulltíða at aldri, þá beiddi hann Loft at gjalda fé þau, er hann hafði at varðveita, er þeir Markússynir áttu, ok Loftr galt féin af hendi, svá sem Gísli beiddi, bæði lönd ok lausa aura.  
When Gísli son-of-Markús was full-grown of age, then he asked Loptr to repay that money-and-property, which he (ie Loptr) had in keeping (lit: to keep safe), which they, [the] sons of Markús had-a-right-to (eiga, Z4), and Loptr repaid the-money-and-property from [his] hand (ie out of his keeping), such as Gísli requested, both lands and loose-property (ie roughly equivalent to chattels).