Pronouns are a part of speech that can perform functions of a noun and, therefore, are used very often. Pronouns must necessarily agree with the nouns they refer to, and it is important to remember that some indefinite pronouns can be only plural or only singular, but some of them can be both depending on the situation. It is also important to bear in mind that if there are two nouns joined by a conjunction, a pronoun that refers to them must also agree in number correctly. Always make sure that you do not use pronouns excessively, as it may be confusing.
Using "impact" as a verb has become so ubiquitous I've pretty much given up on this one, but if you want to say things like "The cutbacks greatly impacted the bottom line" know that the grammar geeks of the world may cringe. Why? Because "affected" is what you really mean and once upon a time "impact" was used strictly as a noun. Maybe you've never mastered the difference between "affect" and "effect" and use "impact" just to be safe. If that's you, it's time to understand these words now. "Affect" is a verb that means to do something that causes an "effect," which is noun. Just think of the "a" in "affect" also is used in "action," which is what verbs do.