To travel from France to Germany by train, use a route either via Paris/Lille to Cologne by Thalys train. Or from Paris via Strasbourg/Saarbrücken to Frankfurt or Stuttgart by TGV/ICE. There is also a direct train from Marseille in direction of Frankfurt. Please use the given booking links to find schedules and ticket prices. Prices are usually the same, but sometimes vary slightly.
If you want to use a night train, have a look at the Russian night train Paris to Moscow (exit in Berlin). A very nice experience and high quality, but does not run daily!
The Europe Special price of Deutsche Bahn (German railways) is available from EUR 39. As earlier you book, as cheaper the ticket prices are.