Flying the Eindecker is more than on any other plane a question of "energy management".
While the later planes all gain forward speed/energy from their engines, the Eindecker's is rather poor. But here you will learn the most about flying.
For any movement you want to perform, you must gain energy. So, if you want to make a turn: keep nose below horizon before / gain energy.
If you want to make a tighter turn, you may even have to dive a bit, to gain more energy.
Climbing after some opponent KILLS your energy rapidly, and makes you a sitting duck very quick. You can't do any quick action, when you have killed the energy.
Keep that in mind all the time. Only climb, when not in any danger. If in action or wanting to perform a manoeuver: nose below horizon - gain speed/energy first.
After a while, you'll get better with that. But: your opponents in here will remain superior - they just have the better fighters; and you must get very good, to get some downed.
That's, why I will play BHaH backwards - I'll start 1918, with the easy plaes, and work my way back to the more humble ones.
The Eindecker will be the last, and the hardest "lesson".