window.addEventListner, functions, IconContext not working in my functional component React

import React, { useState, useEffect } from "react";
import { FaBars } from 'react-icons/fa'
import { IconContext } from 'react-icons/lib';
import { animateScroll as scroll } from 'react-scroll'
import {
  Nav,
  NavbarContainer,
  NavLogo,
  MobileIcon,
  NavMenu,
  NavItem,
  NavLinks,
  NavBtn,
  NavBtnLink
} from "./NavbarElements";

const Navbar = ({ toggle }) => {
  const [scrollNav, setScrollNav] = useState(false);

  const changeNav = () => {
    if(window.scrollY >= 80) {
      setScrollNav(true);
    } else {
      setScrollNav(false);
    }
  };

  useEffect(() => {
   this. window.addEventListener('scroll', changeNav)
  }, [changeNav]);

  const toggleHome = () => {
    scroll.scrollToTop();
  }

  return (
    <>
    <IconContext.Provider value={{ color: '#fff' }}>
      <Nav scrollNav={scrollNav}>
        <NavbarContainer>
          <NavLogo to="/" onClick={toggleHome}>dolla</NavLogo>
          <MobileIcon onClick={toggle} >
            <FaBars />
          </MobileIcon>
          <NavMenu>
            <NavItem>
              <NavLinks to="about">About</NavLinks>
            </NavItem>
            <NavItem>
              <NavLinks to="discover">Discover</NavLinks>
            </NavItem>
            <NavItem>
              <NavLinks to="services">Services</NavLinks>
            </NavItem>
            <NavItem>
              <NavLinks to="signup">Sign Up</NavLinks>
            </NavItem>
          </NavMenu>
          <NavBtn>
            <NavBtnLink to='/signin'>Sign In</NavBtnLink>
          </NavBtn>
        </NavbarContainer>
      </Nav>
      </IconContext.Provider>
    </>
  );
};

export default Navbar;

import styled from 'styled-components'
import { Link as LinkR } from 'react-router-dom'
import { Link as LinkS } from 'react-scroll'

export const Nav = styled.nav`
    background: ${({scrollNav}) => (scrollNav ? 'red' : 'transparent')};
    height: 80px;
    margin-top: -80px; 
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1rem;
    position: sticky;
    top: 0;
    z-index: 10;

    @media screen and (max-width: 960px) {
        transition: 0.8s all ease;
    }
`;

export const NavbarContainer = styled.div`
    display: flex;
    justify-content: space-between;
    height: 80px;
    z-index: 1;
    width: 100%;
    padding: 0 24px;
    max-width: 1100px;
`;

export const NavLogo = styled(LinkR)`
    color: #fff;
    justify-self: flex-start;
    cursor: pointer;
    font-size: 1.5rem;
    display: flex;
    align-items: center;
    margin-left: 24px;
    font-weight: bold;
    text-decoration: none;
`;

export const MobileIcon = styled.div`
    display: none;

    @media screen and (max-width: 768px){
        display: block;
        position: absolute;
        top: 0;
        right: 0;
        transform: translate(-100%, 60%);
        font-size: 1.8rem;
        cursor: pointer;
        color: #fff
    }
`;

export const NavMenu = styled.ul`
    display: flex;
    align-items: center;
    list-style: none;
    text-align: center;
    margin-right: -22px;

    @media screen and (max-width: 768px) {
        display: none;
    }
`;

export const NavItem = styled.li`
    height: 80px;
`;

export const NavLinks = styled(LinkS)`
    color: #fff;
    display: flex;
    align-items: center;
    text-decoration: none;
    padding: 0 1rem;
    height: 100%;
    cursor: pointer;

    &.active {
        border-bottom: 3px solid #01bf71;
    }
`;

export const NavBtn = styled.nav`
    display: flex; 
    align-items: center;
    

    @media screen and (max-width: 768px) {
        display: none;
    }
`;

export const NavBtnLink = styled(LinkR)`
    border-radius: 50px;
    background: #01bf71;
    white-space: nowrap;
    padding: 10px 22px;
    color: #010606;
    font-size: 16px;
    outline: none;
    border: none;
    cursor: pointer;
    transition: all 0.2s ease-in-out;
    text-decoration: none;

    &:hover {
        transition: all 0.2s ease-in-out;
        background: #fff;
        color: #010606;
    }
` ;