As CF would say “cock the foot” and step down not out, quickly.
Often, when some athletes accelerate, they will pick their back foot up higher than necessary and then step forward. Ideally, you don’t want to allow your first step to hang in the air longer than is needed so get the foot down soon. As you mentioned, part of the equation is being very active and early with the arms but don’t hang your first step up in the air (for lack of a better term) since it will likely cause your first step to be too long.
If the first step is at all an issue now, you can, in some cases, improve the steps that follow it by creating a new rhythm.