first down ...

Question
if a ball carrier carried the ball pass the first down marker, then ran back behind it to try to gain more yardage, then he got tackled behind the first down marker. Did he make first down?

Thanks,
Thuy

Answer
Thank you for your question.  The answer is No, it is not a first down.  You question deals with forward progress.  The runner in your question advances beyond the line to gain, but "then ran back behind it [the line to gain/first down marker] to try to gain more yardage".  In this case he gives up the line to gain as he is on his feet trying to gain more yardage and in so doing he reverses his advancement and the ball is placed at the spot where he is tackled.