The differences in people is huge many times. I remember I was at about 35k of the 50k heading into the last loop and watched the lead runner heading to the finish line and it looked like he was barely working. I was dragging ass and still had 15k left to go.

The farm has done me well at keeping strength but my endurance is not the best. I've kept my hiking legs with paragliding but really need to get my ass running again.

A good option for training is finding some 5k races near you to enter. Small goals lead to bigger goals and it's not about winning but the training and experience of it.