> Njáll svaraði: "Margir eru þess (P, genitive) vinir mínir (P, G, nom
pl goes together with margir – seems to be lots of these complicated
constructions for the subject in this text), maklegir að eg leggi til
það sem

> Njál answered: My many fiends are deserving of that, that I proffer
that which


Or maybe: "There are many friends of mine deserving of that..." MM &
HP: "I have many friends who deserve good advice from me."


> slota hatt þinn (pull it down over his ears or something else?)


Presumably it's to hang down to hide his face, and thereby his identity.


> Þá mun eftir spurt
> Then (it) afterwards (be) asked

'spyrja eftir' "to ask, enquire" (rather than "ask afterwards").
Compare English expressions like "ask after", "seek after". 'mun'
often = "will be".


> rekur aftur kaup sín oftlega og flýgur á menn

MM & HP: "is apt to cancel a sale and assault people"