Alexander Koryagin:

AK> "When I was 20 I lifted a weight 300 kilograms!"
AK> "That's impossible, even a world record-holder didn't do it!"
AK> "But I lifted. Although I hadn't lifted it."

I see that you hid your question in the subject, forgetting
that it is the extreme summary of the body, rather than an
opening sentence:

         A joke. Is it understandable in English?

Yes, I think that joke can be rendered in English:

-- When I was twenty I was lifting 200 kg!
-- Impossible! Even the world record is below that.
-- Yes I was lifting that weight, although I never lifted it.

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