I won't go into Liberia's history, but if you don't know how the Republic was formed you can read about it here. The freed slaves who settled here brought with them an American style government, religion, customs and of course English. The English was mixed over the years with the tribal languages (or dialects) from the 16+/- indigenous tribes to get the Liberian English that they have today.
Liberian English has a few basic differences that stem from this mixture. The first is the dropping of all hard sounds at the ends of words. A word like "Plate" would sound more like "Play". A name like "Amos" becomes "Amo". All of the local dialects had similar language patterns. A look at the names of the tribes and cities shows the tendency to end in vowels, tribes like Kpelle, Kissi, Bassa and cities like Ganta, Gbanga, and Kakata. Other typical differences are using a hard "T" sound for "TH" (Thinker's Village nearby ELWA is Tinker's Village for example). The "sk" combination comes out as "ks" typically (ask sounds like aks or ax).
There are some words that were used back in the 1800's that America has long since dropped, but Liberia still uses. You'll see a little more about that below.
Another common expression is to add an "-oh" at the end of a word for emphasis. Such as "The weather is hot-oh" or "I sorry-o". Below are a few other expressions that are common in Liberia, but a little different than the usage in America, or just seldom used in America anymore.
(note - my examples are in American English rather than trying to spell out the words as they actually sound)
embarrass - to bother - "I don't want to embarrass you, if you're busy now I can come back later"
guaranteed - better quality - "Don't buy that widget, it is not guaranteed" Note that it has nothing to do with a warranty or any vendor standing behind the product.
so so so - similar to how we'd use blah blah blah or "he said this and that".
so so - all, consistent or similar - "The Oettels and Balls have so-so girls" or "the yard is so-so sand"
so - that direction - typical when giving directions "go so" while the person talking indicates a direction.
ever since - a non specific unit of time - "That house has been that way ever since" with since always the end of the sentence...no length or timeframe is given.
small - can be used meaning a little, such as "move the board small more" or often used as an answer when someone asks how they are doing "trying small"
vexed - same real meaning as in US, it is just used often here whenever someone is angry.
reaching - leaving or going - "OK, I finished here and I'm reaching". Or if someone is reaching, you can be kind and "carry" them in your car.
finished - gone - "the fuel is finished"
dress back - move back
Current - power - "My phone has no current" (or current is finished)
Dry/reducing - skinny/losing weight
Boots - shoes, especially soccer cleats.
Slippers - flip flops
Plat - braid hair
Rogue - thief
Take time - be careful
Hold your foot - I beg you. Beg is also used plenty in Liberian English.
After living here a year I understand people...most of the time. Sometimes I still struggle and think I haven't progressed much in my learning, until we have visitors. Having my brother and sister in law and parents visit and struggle to understand things helps to realize how far my comprehension has come.
There are a series of Liberian English videos on Youtube that you can check out. If you go to the fathers advice to his son the chicken rogue you can go to other videos on the sidebar.