Are you asking "why is the deficit becoming smaller?" or "how are they going to overcome the money already lost on D+?"
If it's the former, the answer is simple: continue to raise prices. If they can do another price hike (already announced for later this year) and keep western subscriptions steady that should be close to getting breakeven or even making a profit. Introducing a commercial tier in Europe will also bring in additional revenue. And, on that note, if price hikes inspire people to go from ad free to the ad tier, it actually is better for the company as they make more money from the ad tier subscribers.
As for the latter, the answer is simply that they need to start making a profit first, then over time it would make up for the invested money (in theory).
Netflix has been profitable lately and they are a higher cost service than D+ and just getting to the same sub rates at Netflix would get D+ into the black as well.