Here’s my translation

Alan

Getr hann nú um síðir losat sik, stendr nú á fætr ok sér, at hin skessan er búin at koma hinum báðum undir sik.
He is able now at last to free himself, stands now on (his) feet and sees, that the-other (hinn, Z1) giantess is ready to bring (koma + dative) them both under herself.

Grípr hann nú undir kjálka hennar ok setr hnén við hrygginn ok brýtr hana svo á bak aftr,
He grips now under her jaw-bone and sets (places) the (his)-knee against the (her)-spine and forces her back (brjóta á bak, Z7) backwards,

en í því hljóp úr henni svo vond gufa framan í hann, at hann rauk út af ok vissi ekkert af sér um stund.
but at that (moment) leapt (spurted) out-of her such a bad (foul) vapour from-the-front into him (into his face?), that he was-driven (recoiled, rjúka, Z2) out from (it) and knew nothing of himself (ie lost his senses) for a while.

En Einarr komst nú undan henni ok náði sverði Hrana ok hjó af henni hausinn,
But Einarr escapes (lit: brings-himself from under (away)) from her and got-hold-of (the) sword of Hrani and hewed off her skull,

en hún hafði bitit Gest á barkann áðr, ok var hann dauðr.
but she had bitten Gest on the-weazand (wind-pipe, oesophagus - what a great word!) already, and he was dead (not so lucky now, having contributed bugger all to the struggle)

Ferr nú Einarr at vita, hvort Hrani er lífs, ok raknar hann þá við. Var honum mjök óþægt.
Einarr now goes to see (vita, Z3)whether Hrani is alive, and recovers his senses then. (It) was much vexed with him (Hrani) (ie Hrani was greatly troubled)

Sækir nú Einarr vatn ok gefr honum.
Einarr goes-to-fetch now water and gives (it) to him.

Svo batnar Hrana smám saman víman. Birtir nú hríðina, ok kemr gott veðr. Vóru þeir þar um nóttina,
So the-giddiness (víma, CV) improves for Hrani (ie Hrani recovers from the-giddiness) by degrees (bit by bit). (It) clears now the-snowstorm (impers , ie the snowstorm clears up) and good weather comes. They were (stayed) there during the-night

ok daginn eftir dysja þeir Gest ok þær í öðrum stað. Heita þar síðan Skessudysjar.
and the-day after (ie next day) they bury Gestr (in a cairn) and those (giantesses) in another spot. Afterwards there (ie that place) is-called Skessudysjar (Cairns-of-the-Giantesses).

Eftir þetta fara þeir at leita hellisins, ok um síðir koma þeir at gljúfrum nokkurum.
After this they journey to look for the-cave, and at last they come to a certain rocky-ravine.

Var þar hamarr stórr ok illt atgöngu. Sjá þeir undir hamrinum, hvar skugga bar á í einum stað. Klifra þeir nú ok vaða þangat.
A large hammer (precipice) was there and (it was) difficult of intrusion (ie hard to get passed, illr + gen, Z2). They see under the hammer (precipice), where (it) bore a shadow (ie a shadow fell)  in a certain place. They climb now and wade (through the snow?) thither.

Er þeir koma þar, eru þar dyrr ok hurð í hálfa gátt.
When they come there, (there) is there a doorway (gramm plural) and (the) door in half (the) doorsill-rabbet (ie half closed, if not half open (gátt, CV)

Ganga þeir nú í hellinn ok inn eftir honum, þar til þeir finna enn nú dyrr ok járnhurð fyrir.
They go (on foot) now into the-cave and inside along it, until the find now yet (another) doorway and an iron-door in-front-of (facing, confronting?) (them).

Nú heyra þeir stórt hrot, svo eigi þóttust þeir þvílíkt heyrt hafa. Leitast þeir svo við at komast inn ok geta eigi,
Now they hear a great howling (cf hrot-garmr, Z1, but ‘snoring’ seems likely in the context), so they bethought-themselves suchlike not to have heard (ever before). With such (svá við, as a result, accordingly?) they search-for-a-way to bring themselves inside and (but) are not able,

ganga svo báðir á hurðina í senn sem vaskligast, þar til hún hrökk upp.
both go (on foot) thus to the-door at-the-same-time as valiantly-as-possible (sem + superlative), until it (the door) was-thrown open (hrökkva upp, CV).

Var þar nú bjart nokkut sakir glugga, er á berginu var austan til. Í því vaknar karlinn, ok var hann næsta stórr ok illúðligr.
(It) was there now somewhat bright by-reasons-of ‘windows’, which were on-the-eastern-side in the rock (precipice). In that (moment) the old-man (karl, Z3) wakes-up, and he was rather (ie very) big and grim.

Hann spyrr, hvat um sé hark þetta ok sagði: "Hefði gesta von verit hér, þá hefði ek sagt mannaþef í helli mínum,
He asks, what this commotion is about and said: “Had (there) been an expectation of guests here, then I would-have reported (declared, sworn) (the) smell-of-humans (was) in my cave,

ok ills hafa mér gefizt draumar í dag, eða hversu gekk ykkr reisan, ok færið þit mér höfuð Hrana?"
and dreams have-proven (gefast, Z8) for me of a bad (kind) (not sure why the use of genitive, ills?) today, so how went the-journey (reisa, CV) for you-two, and did you-two bring to me the head of Hrani? (the poor old man’s a bit confused)”