(Solved) Error ‘npm ERR! ERESOLVE unable to resolve dependency tree’ and & How to fix NPM warnings

Problem: Error ‘npm ERR! ERESOLVE unable to resolve dependency tree’ & Warning: How to fix NPM warnings

Error Solution:

1. Remove the package-lock.json and node_modules files
2. Install these old packages with npm install --force
3. run npm outdated
4. see what packages are in red
5. do upgrade from the current version to the wanted version with npm install --save packagename@wanted_version  or open the package.json file and change with wanted version and run npm install

Warning Solution:

6. If there is a warning, update it again with the latest version according to the above order.

Fixed the problem.