I know about this thread. Nevertheless, I am unable to find that header.tpl file and, in general, clear instructions on how to achieve the goal of having both the logo and the journal-title at the same time in OJS3 for a multilingual website.
If you are planning on modifying a .tpl file, it might be best to modify it as part of a child theme that you create (based on the existing theme that you’re using), rather than modifying the theme files themselves. You may want to look at our theming documentation: Child Themes