The name means "Old Corellian" and it was superceded by modern Corellian about 500 years before the "present" in swtor (so, VERY roughly: 500BTC or 4000BBY).
Olys Corellisi is like the bastard step-child of conlangs in the Star Wars EU. It's only ever used in bits and pieces, and it's pretty apparent that there's no specific standard for it set for the EU authors... it's got clear roots in several real languages but doesn't adhere to any of them (or to itself), so I will do breakdowns from the canon where possible but most of the actual usage rules will need to be generated from scratch and will be kept minimal.
An interesting discontinuity is that Olys Corellisi is supposed to have survived on Socorro... which was not colonized by Corellians until about a thousand years after Olys Corellisi is supposed to have died out. In the time of SWTOR, Olys Corellisi is still used by scholars (as we would use medieval Latin), and by smugglers and pirates as a sort of secret language.
Canon words and info are in green.
Since it's supposed to be related to Basic, I tend to consider pronunciations that lean toward the English word it's taken from. So Khoengh is much like king or khayng, gylif much like wlife or wliff.
Given the way this seems to be thrown together at random, it's no surprise that the language doesn't show much (any) inflection. Valle is "you" whether it's subject, object, or possessive ("your"). That means that word order will be paramount in contextual meaning, and it seems to more or less follow English phrasing "The door is red" will be "Uhl port ets chirq" not "chirq uhl port ets," for instance and "Uhl Pyroni fhars Vinthern" is very different from "Vinthern fhars uhl Pyroni."
There's a very good meta-translator called the Coruscant Translator that includes all the canon terms and then uses letter-replaced Esperanto to fill in any unknown words. It's an extremely useful tool if you're using it with someone else as you can give them a conversation ID and then you can see what each other translates, and the letter analysis used to pick replacements is outstanding, but the translations for certain words only found in phrases lacks nuance (as is to be expected for a tool like this) and may not match what others are saying if they're not using the translator too but going off a word list. If you just need something quick, or to carry on a long and detailed conversation with another player, I suggest this translator.