@GoGo has solid advice. Try really, really hard to stay above 1,000 words and below 2,000 words. Readers on this site have incredibly low attention spans.
GoGo's advice on update frequency is also accurate. Readers (and Webnovel) want frequent, predictable updates. I believe Webnovel will ask you to post at least 1,000 words per day if you get a contract with them (and will really want you to post at least 1,500 per day), so you'll need to get used to publishing much more quickly if you want to get a contract.
Of course, publishing much shorter chapters will make that easier to do.
On that same note, you also need to use shorter paragraphs. You shouldn't be going above 70 or so words for your longest paragraphs, and should cut them even shorter whenever you use complex sentences. 350-word paragraphs will simply lose the attention of most readers here.
Whenever you have a change in narration topic, at the very least, you need a new paragraph. In your first chapter, you have a long paragraph which starts by describing the MC's mental state, then his physical features, then his clothes, then the city guard, then the master of the city, under the umbrella of giving context for the MC's clothes.
Even without editing the actual content of that paragraph, it would read much, much better if you cut it up into small chunks like this:
He was a young boy at the age of fourteen, and he was extremely thin because of his lack of activity after his sister died.
He had been depressed and sad to the point that it affected him physically, further deteriorating his body. On top of already being extremely small for his age, he would now have a malnourished body and was extremely thin.
However, he could be said to be handsome if he was not so thin.
He had beautiful blue eyes and jet black hair cut short. The robes which he put on were a silvery blue in color, and although they were not of high quality, they were not of low quality either. On the front of them was a small patch with a small silver sparrow silhouette on it. Below the sparrow was a single bronze star representing his rank.
A single bronze star was the lowest rank above commoners, and it was not at all powerful in the city.
The city was called the city of silver sparrow, famous for its silver sparrow guard, which were all extremely powerful with three silver stars each. They were the city's last line of defense and had always been the trump card of the city of silver sparrow. The silver sparrow guard was made up of five members and all of them had strength only below the city master, who was the strongest person in the city.
The city master was the only one in the city to be ranked at one gold star. In total, there were three bronze stars, three silver stars, and three gold stars. Those at the three star gold ranked warrior level were known to be invincible and they were not someone that anyone could kill.
You're also redundant with a lot of your description, like telling us three times in less than 80 words in the above section that the boy was thin, or by just repeating basic details and actions very closely together:
As he walked out of his room, the boy heard his mother's voice. "Su Tao, I made breakfast. Come eat," The boy's name was Su Tao, and he went up to the table and ate.
Or like this bit from the next chapter:
As he got into the water, he winced in pain since it was still extremely hot, and even though it wouldn't burn him, it would still cause him a tiny bit of pain, and on top of the pain from his aching muscles, it was very painful.
But the pain went away very quickly and soon relaxed his muscles.As his muscles relaxed in the hot water, the pain lowered to a tolerable point so that he could train again.
Your first chapter is just describing the MC being a depressed kid with a mother who loves him, as well as describing the setting. 5K words is way too much for this. Readers want to see some kind of action or forward momentum in the first chapter.
An opening is your chance to promise the reader what kind of story they're about to read, and having a depressed MC who does nothing is probably the single worst kind of opening you can make.
Keep in mind that, by the standards of this site, a reader would have read two to four chapters of another story by the time they finish your first chapter, and during that time, there is no plot progression and the MC shows neither any power nor any virtue that will make a reader cheer for him.
My suggestion is to remove the current first two chapters and make a new first chapter with the following plot:
Su Tao shows up to the training ground. People talk behind his back about him as he sets up to train. Someone has pity for him because he has become depressed and weak after his sister's death. Someone else mocks him for his weakness. A third person chastises the second person, saying that Su Tao is showing mental strength by forcing himself to train even though he's depressed and weak.
Su Tao ignores the people talking about him, only focusing on training. The pain he feels is much greater than before, because his body has deteriorated, but he forces himself to push through the pain and train harder than he ever has before. He imagines that he is striking the face of the young master who killed his sister, and this makes him punch harder and faster until he is at the point of exhaustion. He falls to the ground.
Su Chao comes over and mocks Su Tao to his face for being so weak that a training dummy could defeat him. However, Su Tao ignores him, gets back up, and keeps training.
Su Chao attacks Su Tao, and your chapter continues as normal, ending with Su Tao being struck by lightning as your chapter currently describes.
All of that should take no more than 2,000 words. You shouldn't give all the details of the city right away, but give details over many chapters as the details become relevant. Readers care about characters much more than they care about the city and the guards.
I also highly recommend you use the free version of the ProWritingAid software to help edit your chapters. PWA is much better than Grammarly.
Also, please don't tell your reader the story isn't good in your synopsis! You want to convince them it is worth their time, not tell them they have to sit through a bad story for a while until it gets good. Just start with the good part.
Here's a better version of your synopsis:
Destiny is unpredictable.
No mortal can tell how, where, and when any event might occur.
This is especially true for poor Su Tao, a young, talentless boy in a city of bullies and thugs.
When the city's young master humiliates and murders his sister, Su Tao loses all hope.
He has forgotten the words his sister once lived by: "Never give up hope. So long as you hold on, there's always time for a miracle."
That miracle has come...
...and now Su Tao is the strongest abomination this world has ever seen.
I'm an editor, so feel free to ask any more writing questions you might have, and I'll try to answer them!