Here’s my translation

Alan

Þrællinn spyrr nú, hverr gaurr svá firna djarfr er, at slíkt lofar sér at gleypa. 
The-slave asks now, which rough-fellow is so very daring (firna-djarfr, Z), that permits himself to gulp-down in-such-wise. (whatever that means)

Herrauðr bað hann þegja, fúlan slána. 
Herrauðr bade him be-silent, (the) foul lanky-fellow („Shut up, you great streak of misery!“).

Þrællinn sló með stórri kylfu til Herrauðar, en hann brá við skildinum. 
The-slave struck with a large club at Herrauðr, but he warded (it) off with the-(his)-shield (bregða e-u við, Z7)

Höggit var svá þungt, at hann brotnaði allr. 
The blow was so heavy, that it all (ie the whole shield) was-broken.

Herrauðr hljóp undir þrælinn, en hann tók fast í móti, ok váru þeira sviptingar sterkligar, ok fór þrællinn hvergi á hæl. 
Herrauðr ran under the-slave, but he held fast in return (ie offered firm resistance) and their tussles-were strong-looking, and the-slave went by no means on (his) heal (hæll) (ie did not take a single backward step)

Bósi kom þá at ok tók fætrna undan þrælnum, ok lögðu síðan snöru á háls honum ok hengdu hann þar á eikunum.
Bósi came then at (him) and took the-legs from-under the-slave, and placed after-that a halter on his neck, and hanged him there on the-oak-trees (looks  fem dat plural to me).

Síðan setti Bósi konungsdóttur á handlegg sér ok bar hana til skips, ok létu frá landi ok fóru þar til, er þeir fundu Smið. 
After-that Bósi sat (the) king´s-daughter on his forearm (tucked her under his arm?) and bore her to (the) ship (formerly the boat), and (they) left from land and journeyed until they met Smiðr.

Konungsdóttir barst lítt af, en þegar Smiðr hafði orð við hana, tók af henni allan óhug, ok sigldu heim í Gautland.
(The) king´s-daughter bore herself poorly from (it) (ie she was wretched, much cast down, berast, Z.i.6), but as-soon-as Smiðr had a word with her, (it) took from her all glumness, and (they) sailed home to Gautland.

14. Frá bardaga.
14. About (the) battle.

Þat byrjast nú, sem þeir bræðr höfðu fullbúið sitt lið ok höfðu ógrynni liðs. 
That was-begotten now (ie It was now brought about, byrjast, Z3, passive), that those brothers (ie Sigurðr and Siggeirr) had fully-prepared their troops and had an immense-quantity of troops.

En svá hafði Goðmundi konungi orðit þungr pústrinn Herrauðar, at hann var eigi ferðugr at fara þessa ferð, ok skyldu þeir bræðr hafa af veg ok vanda. 
But (And) Herrauðr’s box-on-the-ears (nominative) of King Goðmundr had become (ie been) so heavy, that he (ie the King) was not travel-ready to travel this journey, and those brothers should have (the) way (direction, control?, vegr, Z2,3) and (the) obligation (responsibility, vandi Z2, 3) of (it, the journey? not sure the role of af here?). (ie as result of the king´s incapacity, the brothers would have both control over and responsibility for the expedition)
(vegr ok vandi seems like it must be a set phrase but I could find only one other occurrence, see https://books.google.com.au/books?id=GwEYAAAAYAAJ&pg=PA231&lpg=PA231&dq=%22veg+ok+vanda%22#v=onepage&q=%22veg%20ok%20vanda%22&f=false )

Þeir höfðu fjóra tigi skipa af Glæsivöllum, en juku þó mörgum við í ferðinni. 
They had forty (lit: four tens of) ships from Glæsisvellir, but (and) (they) added nevertheless many (more) in the-journey.

Þeir kómu til Bjarmalands ok fundu Hárek konung, föður sinn, ok váru þeir Herrauðr ok Bósi nýfarnir þaðan. 
They came to Bjarmaland and found (met) King Hárekr, their father, and they, Herrauðr and Bósi were recently-journeyed from-there (ie they had just left).

Hafði Hárekr konungr þá fulla vissu af því, at þeir höfðu tekit í burtu dóttur hans. 
King Hárekr had then full certain-knowledge (noun) of that, that they had taken away his daughter.

Hafði hann þá búit lið sitt ok hafði fimmtán stór skip. 
He then had his troops readied and had fifteen large ships.

Slæst hann nú í ferð með þeim bræðrum, ok höfðu þeir alls sex tigi skipa ok sigla nú til Gautlands.
He joined now in (the) journey with those brothers, and they had in all sixty (lit six tens of) ships and (they) sail now to Gautland.

Nú er at segja af þeim Herrauði ok Bósa, at þeir safna liði, þegar eð þeir koma heim, ok vildu vera búnir, ef þeim væri eftirför veitt, en halda þá brúðlaupin, er gott tóm væri til. 
Now (one) is to say of them, Herrauðr and Bósi, that they assemble troops, as-soon-as they come home, and wanted to be ready, if a pursuit was mounted (veita, Z7) for them, but (and) to then hold the-wedding, when good leisure existed (ie when there was some free time for it).

Þvari karl hafði látit smíða spjót ok öxar ok örvar, á meðan þeir váru í burtu, ok kom þar nú saman mikit fjölmenni.
Commoner Þvari had caused to make spears (probably plural) and axes and arrows, while they were away, and a great crowd-of-people (men) (nominative) came now together there.