> Austmaðurinn hleypur að honum og höggur framan á brjóstið og þar

á hol.

'hol', neuter = an internal cavity of the body. I don't think it's
saying literally that he made a hole (albeit we can infer that a hole
was made), but that his blow penetrated into Hjort's chest.

> varpar sér skjótt til höggs
> swiftly came to blows

I think you have the right idea although "came to blows" just sounds a
bit odd to me in the context, since they are already on opposite sides
in a battle. Maybe "he quickly/swiftly hurled himself at the
Norwegian (and struck at him)", or something like that.

> "Þess galt eg nú,"
> "This I am now repaid"

Or rather: "I have now paid for that" (þess = gen.sg. of 'þat').

> Þá mælti Starkaður: "Flýjum nú, ekki er við menn um að eiga."

> Then said Starkad "Let us flee for we are not fighting here with men

(the implication being - they are Berserkers and not subject to
ordinary men's weakness)

Or trolls -- something not altogether natural anyway...

> Gunnar mælti: "Það mun ykkur feðgum þykja illt til frásagnar ef ekki

skal mega sjá á ykkur að þið hafið í bardaga verið."

"That will seem bad to you father and son (=you Stakaður and your son
Þorgeir) if it can't be seen from you (i.e. from your wounds) that
you've been in a battle."

'feðgar' "father and son"
'ykkur' dative of 'þið' (old spelling '(þ)it').

> Síðan hljóp Gunnar að þeim feðgum og veitti þeim áverka. Eftir það

skildu þeir og höfðu þeir Gunnar marga þá særða er undan héldu.

> Then leaps Gunnar at them and dealt them each a wound, after that

they broke off And those Gunnars ( G and his brothers) wounded many
that tried to get away (?escape)

"Then G. leapt/rushed at that father-and-son (Starkad and Thorgeir)
and dealt them wounds / a wound. After that, they parted, and G. and
his brothers had wounded many (of those) who fled."

'særða' is masc.acc.pl. agreeing with 'þá' (the men who escaped). The
past participle of a verb used with 'hafa' to express the perfect
tense is usually neuter nom.acc.sg. in prose, but sometimes this more
archaic construction is used where the past participle is accusative
and agrees with the object.

LN