I won't comment on the grammar and spelling mistakes, since many have already spoken about it.
It's amazing how someone can take a good idea for a very good plot and turn it into such a horrible novel. The romance for the MC and the Female Lead is as dumb as possible. He tries to make it an epic romance, but fails terribly. Either they are apart because the FL is a dumb b*tch, or the are together with the FL whining and complaining about the MC. And the poor bastard just takes it, over and over again. This whole idea is so plain stupid that the MC nearly sacrifices his life for the FL so many times, and the times he needs help she is never around because she needs to be stronger for the MC. What is the point of that if she is never around when he needs it?! On the other hand we have another love interest that practically killed herself to save the MC, that stands by him, supports him, understands him, but NO!! The FL has to be the romance for the MC. It gets so annoying that I find myself wishing the stupid spoiled FL to just die. I honestly think the author must have had a really screwed up relation in his past to think of love as he does. Whatever that is, it's not love, neither here nor in hell!!
The characters generally are well written, meaning the are not 2 dimension characters. they have their own backgrounds, reasons, hopes, etc. The issue here is that the author spends as much time writing about the side characters as he spends on the MC. And he keeps on jumping perspectives. One moment we are following the MC doing something important, and then we are watching some non important character doing a monologue about how beautiful the sky is.
The time jumping also is a bit too much. Time travelling is supposed to be either impossible or prohibited by the higher powers, but every few chapters we find another time traveler, or someone with memories about the future.
The really good parts about this novel is when we are following the MC. He is a decently written character, besides his stupidity in romance and the main love interest. But regarding his "cultivation" an advancement the chapters are pretty interesting. And the challenges he faces are well done as well.
Besides correcting the grammar and spelling (FIND AN EDITOR!!) and slowing down the changes of perspectives, all the author would need is a realistic romance or no romance at all and the story would improve drastically...