I know it is a bad Idea, I have someone else package which I'd like to modify, I don't want to use github editor, so I want to modify it directly in vendor/packagename and push it to git and than reinstall it via composer , is there a better way to do it ? also when I modify the vendor package view files it does not take effect, please help
You would have to create a pull request and wait for the author to merge it (if it fits with their plans)
Alternatively fork the package and create your own version.
If the author thought you might want to change the view files then they should have built in the ability to 'publish' the views - that is, copy them to your resources directory.
Have you tried php artisan vendor:publish and see if the package is listed?