Tammy Abraham proved a handful during his first 60 minutes of global football and man of the match Ruben Loftus-Cheek flourished under the Wembley floodlights, as did fellow debutant Jordan Pickford.
"To go to the World Cup it's a long season and I still have to improve".
The 23-year-old Everton 'keeper's highlights saw him twice deny Timo Werner with sublime low saves in the first half, though his display did not come as a surprise to Southgate.
Germany played England in a football friendly earlier this year in Dortmund.
He beamed: "I'm really not surprised by what [the young players] have done because they've shown that previously in other ages and this week in training".
"To go to the World Cup?".
"Tonight it took him 10 minutes to have a look around and think "Alright okay, I can do this".
Every England fan knows from watching Wright as a pundit; there are not many more men passionate about England's national team than him. It was good for us young players and I certainly learned a lot. Obviously against a well-oiled machine they will have periods in the game where they control possession but I didn't think they hurt us.
The 20-year-old has previously played for the Under-16s through to the Under-21s.
"What we've seen is Gareth will pick those players".
Loftus-Cheek was pulling the strings in midfield as England pushed for a goal, including feeding captain Dier to get away a cross that Mats Hummels had to hack behind his own goal.
"I'm pretty confident this England team could stay up".