Your first flight is your shot. Everyone flies the same course that day.
Keep it or mulligan it. A mulligan lets you fly the official run once more. The redo replaces your score, even if it's worse.
Then practice all you want. Practice never touches your stats.
Mulligans: you start with 1 and earn 1 for every 7 days in a row, holding up to 3. Closing the game mid-flight counts as 0. The day resets at midnight your time.