Furia keyawra pamrel, hìtxoa.

[Renten]

Kaltxì, oeyä aysmuktu amip! Soaia oeyä tsawl slìmu nìtxan.

Oeru syaw Renten (tsalì'u oer sunu frato), ulte oeri solalew zìsìt mevomun. Txankrr oe ftarmia lì'fya nìNa'vi, slä ke pamlltxe ayngahu kawkrr. Fì'u fìtrr lateiem! Oeru sunu pamrel tìsusi, tìwuseyn, sì tìronsruselngop ayvurit futa oel ke peng kifkeyit kawkrr alunta oe lu ngong. Ziveyko kxeyey oeyä txo ngal rivun 'uoti, rutxe! (Kop tsayhey leNa'vi lu hona kuma oe tìyerkeiup)

Translation so you know what I was at least trying to say:

Hello, new brothers and sisters! My family just got a whole lot bigger. 

You can call me Renten (it's my favorite word), and I'm 18 years old. I've been studying Na'vi for a long time, but I've never spoken with any of you before. That changes today! I love writing, drawing, and imagining stories that I'll never share with the world because I'm lazy. Please correct my mistakes if you find any! (Also these Na'vi emoticons are so cute I'm gonna die)

(By the way, I wanted my title to mean "excuse my awful grammar" but I don't know how to say grammar sooooo)

So, what about you guys? Läpivawk nì'it, rutxe. I can't wait to get to know all of you!

[Kame Ayyo’koti]

Zola'u nìprrte', ma Renten! Fwa fìsoaia awngeyä ngafa ioi säpoli set lu tìlen aetrìp!*

I would try to correct your postì, but I am still learning myself, and it's late here and I am very tired right now. All I will point out for now is this: As far as I know si-verbs such as «pamrel si» cannot take the form tì- <us>. At least Annis mentions it in his grammar book at §5.1.4.1:

Tì- ‹us› creates a gerund. It is fully productive for verb roots and compounds (si-con-
struction verbs, §5.3.3, cannot be made into a gerund).

But don't agonize over your mistakes—focus on improvements!
Another good speaker is always a good thing! I hope to see you around!

[Renten]

Kaltxì ma Kame Ayyo'koti! Thanks for the tip about gerunds, I suspected it but I wasn't sure. How would you say it, then? My only other idea is to use pamrel, but I feel like there should be a distinction between physical written words (when I imagine pamrel as meaning) and the act of writing. Maybe someone else can give their two cents here, or if not I can ask about it somewhere.

Anyway, it's great to meet you! I'll focus on my improvements once I make a few, but given that I remember as much as I do after barely studying Na'vi at all for at least two years, I'm fairly happy with my abilities. You seem to be pretty good yourself! 

[Tìtstewan]

Kaltxí ulte zola'u nìprrte' fìtsenge, ma Renten!

Maybe someone else can give their two cents here, or if not I can ask about it somewhere.

The gerund of pamrel si is just pamrel.

Pamrel oeru sunu. I like writting.

tì'awm si -> gerund:
Tì'awm lu txantsan. Camping is great.

[Kiyevame Ikran]

Kaltxì ulte zola'u nìprrte' ma Renten

[Kame Ayyo’koti]

Kaltxì ma Kame Ayyo'koti! Thanks for the tip about gerunds, I suspected it but I wasn't sure. How would you say it, then? My only other idea is to use pamrel, but I feel like there should be a distinction between physical written words (when I imagine pamrel as meaning) and the act of writing. Maybe someone else can give their two cents here, or if not I can ask about it somewhere.

Regarding physical writing vs the act of writing, I don't know for sure. «Pamrel» definitely refers to physical writing, but I don't have enough experience to know if it can refer to the act as well. My best suggestion: If you want to emphasize that you mean the act, then use it as a verb and give an example of what you write, like this:
Furia pamrel si ayvurur ayuorsì oer prrte' lu kop.
To write stories and-other-things to-me pleasing is also.
Writing stories and other things also pleases me.

Karyu Pawl manages to create something similar in this post with sunu, so this should work, too:
Fwa pamrel si sunu oer.

Although maybe prrte' is better, as Pawl mentions in another post:

Sunu and prrte' lu both mean that the speaker enjoys something. While sunu is 'like' in the general sense, prrte' lu is generally deeper and more heartfelt; it's often used in social situations, translating to "It's a pleasure . . ."

And already we are discussing things! We should maybe move this to one of the question sections.

Anyway, it's great to meet you! I'll focus on my improvements once I make a few, but given that I remember as much as I do after barely studying Na'vi at all for at least two years, I'm fairly happy with my abilities. You seem to be pretty good yourself! 

Thank you, I'm glad you think so. I want to be as good as I possibly can. As for you, well, now you get to enjoy learning the finer points of using Na'vi.