Sharing steemit exclusive content tends to be better received than translating old work. That's my opinion. You'll practice your English over time as you write more and more.
In the meanwhile, you can participate in photography and music challenges etc.
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I'm just telling from my curation experience on Steemit. You are of course welcome to share your old work. But you'll probably earn more, for example, by recording an openmic entry than by sharing your 3-year old youtube video.
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I know, I rewarded both of those posts. :) And the first one was in spite of it being old, cause it was pretty good and I wanted to motivate you.
That's my approach, other curators may have different approaches, so I guess you are right that you can never know.