Cen Chen,who grew up in Cheng City during his childhood. He regarded the city walls as a treasure. Cen Chen once declared in Cheng City that he would undertake the construction of the city walls. Before that, Cen Chen became an official and indeed took on the responsibility of constructing the city walls.

A sentence like " Cen Chen,who grew up in Cheng City during his childhood" is incomplete feeling, The "who ..." part indicates it's just a modifier to Cen Chen, which means the sentence still needs a verb. You might see this kind of construct as a caption to an image, but not a sentence in a larger piece.

One morning, Cen Chen climbed up the city walls and gazed directly at the patterns that foretold fortunes. As red dust fell, the patterns revealed a sign of disaster, Cen Chen was very angry and punished the person who made the patterns by forcing them to prop up the city walls naked.

You need spaces after commas and full stops.

The people of Cheng City devotedly assisted Cen Chen. They presen(collected?) sand and soil from beside buildings, layer by layer constructing the city walls until the walls toreached towering heights. Cen Chen exerted his full capabilityies and accomplished the construction of the city walls.

Not fully sure what you intended with "presented", so collected is just a guess.

The people of Cheng City said in praised, "Cen Chen is truly loyal to Chengcheng!"

praised X implies that the praise was directed at X, not that X was the praise that was given.

Cen Chen,who grew up in Cheng City during his childhood. He regarded the city walls as a treasure. Cen Chen once declared in Cheng City that he would undertake the construction of the city walls. Before that, Cen Chen became an official and indeed took on the responsibility of constructing the city walls.

always put a space after commas and periods.

One morning, Cen Chen climbed up the city walls and gazed directly at the patterns that foretold fortunes. As red dust fell, the patterns revealed a sign of disaster, Cen Chen was very angry and punished the person who made the patterns by forcing them to prop up the city walls naked.

spaces
I don't know if it's just a typographical error but the e is missing

The people of Cheng City devotedly assisted Cen Chen. They presented sand and soil from beside buildings, layer by layer constructing the city walls until the walls turned into towering heights. Cen Chen exerted his full capabilityies and accomplished the construction of the city walls.

since the capability is plural, then it's "capabilities"

Cen Chen uUndertook the cConstruction of Cheng City

Important words in title have capital letter.

Cen Chen,who grew up in Cheng City, during his childhood.He regarded the city walls as a treasure. Cen Chen once declared in Cheng City that he would undertake the construction of the city walls.Before After that, Cen Chen became an official and indeed took on the responsibility of constructing the city walls.

'After' would make more sense logically.

One morning, Cen Chen climbed up the city walls and gazed directly at the patterns that foretold fortunes. As red dust fell, the patterns revealed a sign of disaster,. Cen Chen was very angry and punished the person who made the patterns by forcing them to prop up the city walls naked.

The people of Cheng City devotedly assisted Cen Chen. They presentadded sand and soil from beside buildings, layer by layer constructing the city walls until the walls grew to towering heights. Cen Chen exerted histhe full capextent of his abilityies and successfully accomplished the construction of the city walls.

The people of Cheng City said in praised, "Cen Chen is truly loyal to Chengcheng!"