I don’t understand how to do the Speedrun.

Make a video of you playing a specific map, then upload the time you get to an IL category. The board is sorted by ascending, so the longest time will be in first place. For the main board category, you need to go through all the individual levels with only 1 attempt at each level and add up all your times at the end of playing through the 19 levels, using a time calculator or some other tool.