Hello @marinDan
To override the system.php file kindly update this line of code in the boot method in the respective Service Provider file.
On the left side, enter the path with the file name system.php; on the right side, enter the path where you need to override the file.
$this->publishes([ dirname(DIR).'/Config/system.php' => dirname(DIR).'/../../path/ofYour/folder/filename_withextension', ]);
After this run the command
php artisan vendor:publish --force
Thanks & Regards