This is a very confusing page. It doesn't really deal with changes
from Old Icelandic to Modern Icelandic - or at least not with any
_attested_ Old Icelandic. This is more like the changes from
late Proto-Norse to modern Icelandic.

> http://www.angelfire.com/punk2/zaocycle/lang/changes.txt
>
> Was there really a word GALANDI which is now LANDI? What does it mean?

"Yes". 'Countryman'.

The form *galandi is not attested but we can presume that the 'ga' prefix
it was present in this case. But back when that prefix was fully alive the
ending was probably different - I'd reconstruct the word as *galanda(n) or
*galande(n).

A better example is probably nautr < *ganautaR meaning 'comrade'. Here we
still have a German word with the prefix extant; Genosse.

An afterthought. The form 'galande' is attested in late Proto-Norse
or very early Old Norse (the Eggjum inscription) but in the context it
seems to be a present participle of the verb 'gala(n)'.

Another afterthought. There is a German word 'Gelände' but it doesn't
mean the same thing.

> What about this fanþ-fann?

Another unattested Proto-Norse form. Verner's law gives us a switch between
the voiced and the unvoiced dental fricative in the verb 'find':

*finþan - *fanþ - *funðum - *funðinaR

in Old Norse the 'nþ' became a 'nn' and 'ð' became a plosive to yield:

finna - fann - fundum - fundinn

which is exactly the same in the earliest _attested_ Old Icelandic as
it is today. It was probably the same when Ingolfr Arnarson came here too.

> And harðr-hraðr - surely the latter is a completely different word,
> meaning fast/quick?

Surely. The idea hear seems to be that one is formed from the other and
attains
a new meaning. There seems to be very little evidence to support that,
however
and in any case those ponderings are probably not useful to a beginning
student
of Old Norse.

Taken as a whole the page seems to be almost intentionally confusing and
misleading
and is probably best ignored in favour of other sources.

Kveðja,
Haukur