Trying to speak English can be difficult especially if it's not your first language. As time goes by, there is bound to be new vocabulary borrowed from other languages and sentence structures.
Let's not forget that English is spoken differently in various regions of the world and it's how an awesome platform like Wattpad brings different backgrounds together.
If you want to attract more readers, then you need to polish your grammar and spelling first before publishing it. Try writing a draft on any typing software like Google Docs, MS Word or Grammarly.
Now, a few things which bug me the most are wonky sentences and typographical errors. It doesn't help that the author would say "sOrRy Muh horrible writing im not purfekt DoNt Liek dOnT rEAd." Now it's fine if they forgot to add or correct something for once, but making the same mistakes all over again just shows the lack of effort in their writing.
Second, failure to capitalize starting letters, have correct punctuations and spacing. There are books with a promising synopsis and cover until you see the writing. Does this sentence end here? Where is the dialogue? Is it 'america' or 'America'?
Third, using dated terms in professional writing. You don't describe your character as a "boomer" using "TikTok" in your story. Your book can at least be considered timeless if you state the time period explaining the current trends.
Fourth, the confusion between "your" (something that belongs to the other) and "you're," (describing the speaker) or "they" (referring to other people) or "they're" (used to describe others).
Fifth, using semi-colons. This is usually used to give a break between long continuous sentences. A good example of this is "I always see Mr. Yamada limping across the street; he suffers from a broken hip." It only becomes annoying when it's used like this: "Mr. Yamada is always limping; he suffers; from a broken; hip."
Wattpad is a great platform where amateur writers can revise their works anytime. It enables people to comment on each paragraph instead of having to do so at the end. As they say, there's always room for improvements.