Change upload permissions for /var/www/media2net/uploads/ either by changing owner with "chown" or by "chmod"
$ sudo chown apache:apache /var/www/media2net/uploads/ $ sudo chmod 755 /var/www/media2net/uploads/
downloaded_file.png already exists in that directory and it's owned by another user, then you would need to change ownership on that file as well.
$ sudo chown apache:apache /var/www/media2net/uploads/downloaded_file.png
This way, it can be successfully overwritten by Apache.