gehe fahre/reise früher nach Deutschland.
The verb is not gehen, a journey is always a Fahrt or Reise apart from the unlikely event of a pure hiking tour.
The sentence is grammatical but it means I go to Germany earlier (than discussed before). You talk about your plans for the future, not about the past.
- Präsens never conveys the past in German.
You have to use Perfekt if you wanted to tell about the past.
habe bin (im letzten Jahr) nach Deutschland gegangen gefahren/gereist.
Here you tell about the past. Perfekt is what people would usually use. You may add additional markers as im letzten Jahr. All those verbs as "gehen" build their Perfekt with sein.
Ich esse Abendbrot später. (better: Ich esse später Abendbrot.)
Ich werde Abendbrot essen.
These are both okay but they mean a different thing. Später indicates you neither do it right now nor in the next minutes. It's delayed. This isn't the case for the latter sentence which simply tells about your plan to eat dinner. You can even combine it:
Ich werde später Abendbrot essen.
This is okay but a bit overblown. Später already tells it's about the future on the semantic level. No need to emphasize it further by using Futur. People may even expect a passive expression (uses werden, too) because of that.