Returning to Schengen after overstaying in Sweden by 12 days

I am in Ethiopia now but I had been Sweden in march 2017. Is was my first time in the Schengen area. And I stayed 32 days, but the duration of stay in my passport was 20 days. Honestly I have misunderstandings of the staring visa date from to until and the stay of duration. In my thinking, I can stay until validation period and I return back my home before validity date. So I applied for another Schengen visa, and they rejected my application because of this reason. So how can I get a Schengen visa again?

Best Answer

It was your responsibility to understand the terms of your visa. You failed. So what can you do now?

Do not apply again until you have a stable, well-paid job where you live. The overstay is a big factor in the decision, so everything else must look good.
Travel to countries near you, without overstays or similar incidents.
Wait a long time before you make the next application.
Be honest in your next application, mention that it was your mistake.

The two big things are time (many years) and a job to return to.