National Express Deutschland is a fully owned daughter company of the British transport company Mobico Group. National Express gained its first regional rail contracts in February 2013 and commenced operations on 13 December 2015 and used to be commonplace on the Ruhr area with their new Bombardier Talent2 trains. Here we see one of National Express' Talent2 trains at the Münster Hauptbahnhof 8.10.2016. But there was a lot of competition and legal battles with DB. When the Dutch state railways German daughter company went into financial difficulties and finally bankrupt, National Express was given to take over the RRX or Rhein-Ruhr Express network and its new trains and they now have a contract to operate the RRX services until at least 2033.
This train is one of National Express' Talent2 trains.
Picture from Münster Hauptbahnhof 8.10.2016 by Ilkka Siissalo.

A National Express regional express train comprised of two Talent2 units is leaving Münster Hbf.
Picture from Münster Hauptbahnhof 8.10.2016 by Ilkka Siissalo.

The Rhein-Ruhr Express RRX was a trade name of Abellio. Here a first Siemens Desiro HC train, Baureihe 462, was being displayed for the first time before it started to run RRX services. RRX is a regional express train services system comprising five lines, mainly following the river Rhein. After the bankruptcy of Abellio Nordrhein-Westfalen, the RRX services have lately been operated by National Express. The RRX services were started first with Stadler Flirt trains, but then later 84 of these Siemens Desiro HC were bought for the RRX.
Picture 1.9.2018 from Essen Hauptbahnhof by the Wikipedia user "Mnfred Kopka". Published under the Creative Commons CC BY-SA 4.0 Deed Attribution-ShareAlike 4.0 International license.

Currently the National Express Talent2 trains have vanished from the everyday life in the Ruhr area, but the Rhein-Ruhr Express or RRX tains are commonplace everywhere and they are operated by National Express. Here we see a Desiro HC, Baureihe 462. The first and last coach are single floor but all middle coaches are doubledeckers.
Picture from Düsseldorf Hbf 17.4.2026 by Ilkka Siissalo.