Writing in the first person takes a lot of skill. When it's done well, it can really bring the main character and the story to life. Readers will truly feel and think like that character, truly live inside your fictional world. But when it's done badly, your writing will feel distracting, confusing...and sometimes, even silly.
It's My World, You're Just Reading in It
Writing in the first person takes a very delicate hand. You don't want to over-load the book with "I." It gets boring when every sentence or paragraph starts out that way, and the last thing you want to create in your writing is repetition. You have to make sure you describe the character to the audience somehow, and that's tricky. You have to remember to see everything through the character's eyes; they probably can't read minds or hear thoughts, so they have to rely on observation alone to figure out what's going on.
But you also have to remember something else when you're writing in the first person, something that many writers tend to forget: you character can't see their own face.
And when authors forget that, it's just bad writing. Here's an example of what you should not do if you're writing first-person interaction:
"Jade, I really hate to tell you this...but you use bad grammar." Lily was afraid to meet my eyes when she told me.
She could tell from my stricken expression that I was upset. We both looked tense as we sat, staring at each other across a chasm of truths.
Stop! There's so much wrong here, it's hard to know where to start. First and foremost, "Jade" in the example above doesn't know what Lily is thinking, or what Lily can tell. But more importantly, "Jade" shouldn't be able to tell that her own expression is stricken because the scene infers that Jade is looking at Lily, and Lily is clearly not a mirror. The main character is also clearly in her own body and relating this experience because she was present inside of it. Therefore, she can't know how her and Lily look as they're having this discussion.
These are some of the reasons why it's so hard to write in the first person. If you're coming at the reader with an "I" perspective, you may not be in a position to make a lot of observations about how "I" look. But there's still plenty of room for description. "I" can still hear my own voice, and "I" can feel my own face. The first-person character will know when they're smiling, or raising an eyebrow, or crying. They may not necessarily know that they look crushed and hurt by something, or that they are glowing with happiness -- observations like this need to come from dialogue with other characters or interaction with a reflective surface.
First-person interaction with another character is a fine art. The best way to write it well is to completely immerse yourself inside your character's world. Really see your scenes unfolding as you write them and literally put yourself in that character's place. This will make it easier to write naturally from the first person and make observations that are actually plausible.