The most natural and the easiest way to achieve coherence is to repeat the key nouns in your paragraph. However, too much repetition of the key nouns may make the paragraph sound boring. So sometimes you can use pronoun synonyms to refer to the noun. When you use pronouns instead of key nouns. make sure that you use the same person and number throughout your paragraph.
Repeating the key noun, and using pronouns or synonyms to refer to it helps
you create paragraph coherence.