the first step is to locate your project folder

then run these commands one by one

npm uninstall react react-dom

then

npm install react@18 react-dom@18

then

npm install --no-audit --save @testing-library/jest-dom@^5.14.1 @testing-library/react@^13.0.0 @testing-library/user-event@^13.2.1 web-vitals@^2.1.0

then

npm start

here what we are doing is uninstalling react19 and installing react18.

or you can go with this YouTube link: https://youtu.be/mUlfo5ptm1o?si=hYHTwc7hApEXzPX5