the word pi means of. but it also redraws the boundaries of adjectives. take this example: kulupu soweli tempo. soweli describes kulupu, and tenpo describes kulupu soweli.
the boundaries are always like this in toki pona. a of type b, of type c, of type d, etc. by itself, it means time of the animal group. but if we put pi between kulupu and soweli, the meaning shifts to group of time animals.
kulupu soweli tenpo is ( kulupu soweli ) tenpo, and kulupu pi soweli tenpo is kulupu ( soweli tenpo ).
now what happens with a sentence like A B pi C D? If c describes ab, and d describes abc, that would mean that the word pi is useless. So most people use it as cd describing ab. so something like lipu ike pi toki pona means bad page of toki pona, not good bad talking page.
this is a bit hard to explain with words, so heres a diagram with the most common uses of pi.
la is definitely the most complex word in toki pona. it relates sentences, and acts a conjunction, apart from taso and en.
lets take this example: mi lape la mi pona. It means i sleep, so i feel good, or i sleep, then i feel good. La means that when statement a happens, statement happens. Or in coding thought: if(a){ b }.B happens because a happens.
multiple la can also be used. Take this example: mi oko e sina la mi pilin pona la sina pilin nasa. It means: i looked at you, i felt good, and you felt weird. If statement a happens and b happens, c can happen. It may take some time to rap your head around la but it is extremely useful
Here is a translation of cogito ergo sum (i think, therefore, i am): mi lon la mi sona. Its literally i am, so i think.
the word wile literraly means to want, or to need; because why would you want something you dont need? but wanting and needing are both future related actions, so wile is usually used for the future.
Example: mi wile e moku or mi moku wile. It literally means i need/want food/eat, but figuritively it means i will eat, or i am hungry.
The tense can also be expressed with "la" expressions. Take these examples: tenpo pini la and tenpo kama la. It literally means finished time, so and coming time, so.
As said in the last part, there are many different ways to say the same thing in toki pona. Thats part of the beauty of it. Take this example i saw somewhere: some person translated pond as telo suli, but a person who lived near the ocean called it telo lili.
But there are also ambiguities. Many people place nimi ken before any verb, as in mi ken moku. But id argue that ken is an adverb or adjective, so i would say mi moku ken. Same with wile; they say its an auxiliary verb, but i argue that its an adverb. But the most important thing about toki pona is being understood.
o replaces li in imperative sentences. technically, you need to use sina before o. but many people omit it, because its implied that the subject is 2nd person in an imperative sentence.