Here’s my translation

Alan

Hann leiðir kvíguna á básinn, en leysir griðunginn. 
He leads the-heifer to the-stall (in the cow-house), and sets-free the-bull

Hann hljóp upp á kvíguna. 
He (the bull) leaps up on to the heifer.

Mosabelgrinn varð léttr fyrir, ok rak griddi höfuðit út á múrinn ok braut af sér bæði hornin. 
The-skin-bag-of-moss became light (collapsed under his weight?or became active, léttr, Z2, ie moved?) because of (it) (ie as a result), and (it) drove (= reka, Z7, impers,) the-head of the bull (dat of “griddr”? Some sort of contraction of griðungr?) (ie the bull’s head was tossed, thrown) out to the-wall, and broke off both the-horns belonging to him (ie both his horns)

Herrauðr greip þá í bæði eyrun á honum ok í granirnar ok snaraði hann svá ór hálsliðinum.
Herrauðr then grabbed-hold of both his (ie the bull’s) ears and the-lips (pl of grön, Z2) and wrung him (not sure what „hann“ refers to?) thus out-of the neck-joint

Þá vaknaði gýgrin ok hljóp á fætr. 
The the-giantess (crone) awoke and leapt to (her) feet.

Í þessu kom Bósi inn í hofit ok bar þrælinn uppi yfir höfði sér á spjótinu. 
In this (instant), Bósi came into the-temple and bore the-slave up over his (sér) head on the-spear.

Gammrinn brá nú við skjótt ok steypti sér ofan ór hreiðrinu ok vildi gleypa þann, sem inn var kominn. 
The-vulture now started off at once (bregða við skjótt, Z7) and hurled itself down out-of the-nest and wanted to swallow that-one (ie him) who was (had) come inside.

Svalg hann nú þrælinn ofan at mitti. 
It swallowed now the-slave down to (ofan) (the) middle-waist (mitti, CV)

Bósi þrýsti þá spjótinu, svá at þat gekk upp í háls gamminum, þar til at stóð í hjartanu. 
Bósi thrust then (þá) the-spear, so that that went up into (the) neck of the-vulture, until (it) stood in the-heart.

Gammrinn setti nú klærnar í þjóin á þrælsskrokkinum ok setti vænghnúfana við eyrat á Bósa, svá at hann fell í óvit. 
The-vulture set now the-claws into the-thighs’-thickest-parts (plural) of the slave’s-carcase and set the wing-joints (væng + knúi ? + hnúfi?) against the-ear (sg) of Bósi, so that he fell into a swoon.

Fell gammrinn þá ok ofan á hann, ok váru hans fjörbrot ógurliga mikil. 
The-vulture then fell also down on to him and its (his, the vulture’s) death-struggles were awfully (ógurliga, adv) great (mikill, adj).

Herrauðr réðst á móti hofgyðjunni, ok var þeira atgangr inn harðasti, ok hafði kerling illa skornar negl, ok reif hún hold hans niðr at beini. 
Herrauðr was-resolved on a meeting of (ie he confronted) the-temple-priestess, and their fighting was the hardest (stiffest), and (the) old-woman had badly shaped (cut) nails (nagl), and she ripped his flesh down to (the) bone.

Þau bárust þangat at, sem Bósi var fallinn, ok var þar blóðugt mjök. 
They (neut = man + woman) bore (carried)-one-another thither to where Bósi was (had) fallen and (it) was very bloody there.

Kerlingu varð hált í gammsblóðinu, ok fell hún á bak aftr, ok váru þá sviptingar miklar með þeim, svá at ýmsi váru undir. 
(It) became slippery (neut sg of hall, adj) for (the) old-woman (fem dat sg) in the-vulture’s-blood, and she fell back onto (her) back, and a great tussle (fem plural) was then between them, so that now-this-one-now-that-one was under-(neath).

Bósi raknaði þá við ok greip höfuð griðungsins ok rak á nasir gýginni. 
Bósi then recovered his senses (rakna við, Z3) and grasped (the) head of the-bull, and drove (it) into (the) nostrils of the-giantess.

Herrauðr sleit þá af henni höndina í axlarliðinum. 
Herrauðr then tore off the-arm (sg) belonging to her (ie her arm) at the shoulder-joint (sg).

Tók henni þá at dafna leikrinn, en í fjörbrotum hennar varð landskjálfti mikill.
The-sport then began (taka + inf, Z7) to thrive for her (whatever that means), but (and) in her death-struggles a great earthquake occurred.

Þeir gengu nú um hofit ok rannsökuðu þat. 
They (ie Bósi and Herrauðr) went (on foot) now around the-temple and ransacked (or simply searched?) that.

Í hreiðri gammsins fundu þeir eggit, ok var þat allt með gullstöfum ritat. 
In the-vulture’s nest they found the-egg, and that was completely written with gold-letters.

Þar fundu þeir gull svá mikit, at þeir höfðu nóg at bera. 
There they found so much gold, that they had enough to carry.

Þeir kómu at stalla þeim, sem Jómali sat á. 
They came to that (heathen) altar (sg), on which Jómali sat.

Af honum tóku þeir gullkórónu, setta með tólf gimsteinum, ok men þat, sem kostaði þrjú hundruð marka gulls, ok ór knjám honum tóku þeir silfrbolla svá stóran, at engir fjórir menn mundu af drekka. 
From him (ie Jómali, or it, the altar, stalli, masc?) they took a gold-crown, set with twelve gemstones, and that necklace, which cost three hundred marks of gold, and out of his knees (kné) they took a silver-vessel so large, that no four men would (be able to) drink (it, ie the great volume) off.

Hann var fullr af rauðagulli.
It was full of red-gold.