The WPML plugin is generally well respected. As always, there will be other plugins so check a few out, compare features and see which suit your purposes best.
Yes, make a child theme. It’s safer than making modifications to the original theme, and makes them easier to undo.
Thanks. It this solution easy? I have no php skills and am a WordPress beginner. So, I am looking for something I can easily install en presto, it works…
WPML is a plugin, so you’re not doing any coding. You edit everything via the dashboard. But it’s still something else to learn.
Making a child theme – fairly simple, or as complex as you want it to be. See https://codex.wordpress.org/Child_Themes
Sorry about the noob questions, but does this app make the site multi lingual? Or do I need to do something in the dashboard to get the website to support multi languages?
You need to visit the plugin’s website and read about it. All the information you need to find out is there.
But essentially, in the WordPress dashboard, for every page you create you can also write versions in other languages.
The visitor can then select which language they prefer to read the site in.
Obviously, you have to provide the actual translations – the plugin provides the means to manage the page versions.