Solution: storage/logs/laravel.log" could not be opened: failed to open stream: Permission denied

This is my solution.
First you need to run php artisan cache:clear from the project directory, then chmod -R 777 storage or chmod -R 777 app/storage and finally composer dump-autoload and now it will be working fine..
illegal group name actually means that the group you're specifying(after www-data going username).You need to either create the group, stop specifying a group, or specify a group that exists.