While in the translation editor, you can use the icon that will copy the content from the left to the right so that you can quickly get the translation into a "finished" status. Then save.
Then, from the top of the backend of your WordPress site, switch to the language your translation was created in and while you make sure that you are in the backend, with that language selected in the top bar, you can go to "Posts" > delete the post (the translated one) > and also make sure that you removed it from the trash, too.
After that, you can switch back to the default-language backend by selecting that language in the top bar area and re-start the translation.