There is something I can't understand with regards to the {latlh}.

first, lets read these canon examples:

{reH latlh qabDaq qul tuj law' Hoch tuj puS}
the fire is always hotter on someone else's face

{latlh HIvje'Daq 'Iw HIq bIr yIqang}
pour the cold bloodwine into another glass

I want to ask:

1. the {latlh qabDaq} and the {latlh HIvje'Daq} mean ONLY "the face of
another" and "the glass of another" respectively, or do/can they mean
as well "an additional face" and "an additional glass" ?

It can mean any or all of these. latlh means all the things associated with other, another, and additional.

latlh qab
another face
another's (someone else's) face
an additional face

latlh HIvje'
another cup
another's cup
an additional cup

Which meaning you get from it depends on context.

In case you wonder why I'm asking..

Suppose I want to say "for us there is an additional enemy", so I
write {maHvaD latlh jagh tu'lu'}. Does this klingon sentence mean
indeed "for us there is an additional enemy", or does it actually mean
"for us there is an enemy of another", which doesn't make sense ?

What does the context say? Out of context, I'd probably assume the additional meaning, as in "for us there is yet another enemy (which hasn't been discussed before)."

But suppose enemies were being matched up. "For you there is your enemy; for Bob there is Bob's enemy." Then we want to make the point that our enemy is not whom you'd expect. maHvaD latlh jagh tu'lu' for us there is someone else's enemy.

Sure, that's pretty contrived, but it illustrates that it's not impossible to take another meaning based on context.

-- 
SuStel
http://trimboli.name