"Ik heb mijn eerste marathon gelopen."
Translation:I have run my first marathon.
Lopen = to walk. Sports contests are an exception, lopen is used in stead of rennen (also for sprint distances). I'm not sure why, maybe a short form of hardlopen.
Ahh op die fiets. I knew lopen was walk, that's why I was confused as to why it translated into the sentence as ran. Wasn't aware it was an exception in sports! Bedankt :)
Say you did actually walk your first marathon (which is still a non-trivial accomplishment), how would you say that?