It usually means you'll have to use metro.

For which journey is this? (route, date, departure time)

That's wrong. According to DB, the replacement buses stop at Trier station.

You may also want to update your app. My app (version 31.7.0) just says "Change trains”.

Ok, I have activated my pass and used three days.  Is it possible to update the app? I mean that update wont loose anything( oersonal data)

Sure it's possible to update the app.

Now I have updated my app and I have the same version now. Still it looks the same…I mean the transfer by public transport.

Anyway, as Trier Hbf bus station is logically situated next to Trier Hbf (train station). There’s absolutely no need to take other public transport, as it’s just a 20 m walk to the entrance of the train station. Nothing to worry about.

But weird still, it shows like that in your app. Here all good as well.

Ok, thank you for answers. I guess that I am able to use interrail ticket to get in to bus from Luxemburg to Trier?

Yes, because it’s a rail replacement bus since there are engineering works on the rail line.

More info:

https://www.cfl.lu/en-gb/works#renovationsCollapse-1