It takes several weeks of off-and-on practice to master the various knife techniques, but once learned they are never forgotten.

你要花上数周的时间不时地练习练习才能掌握各种刀法技巧，但一旦学会就再也不会忘记了。

youdao

Jun: I took a climbing class once and learned how to belay and tie knots, but I've never seen anything like this.

小君：我上过一次攀岩课，学会怎么做制绳确保和绑绳结，但是我没看过像这样的。

youdao

But once I learned to trust him you can imagine his efforts!

我一学会信任他(你可以想象他的努力！)

youdao

Mr. Burr said that the FBI told lawmakers it had been in contact with the Russians about the brothers "at least once" since 2011, but didn't elaborate on what information was learned.

WSJ: Boston Bombing Suspects Roused by Jihadist Thought

Bob Marley once told Chris, "My father was a ship's captain, " but Chris later learned that tale was untrue.

NPR: Bob Marley's Music and Magic Endure

But once those players finished playing, they could return to the jobs they'd had before because they had already learned the skills they needed.

BBC: Young rugby league stars told to prepare for retirement