MXGP 2020 - The Official Motocross Videogame

Go to quick modes and then championship, set the track to FAST CASH XP (by itchyfawn433243) or any other similar XP/cash custom track, and do the same track for all 20 slots or however many you want to do in your championship and repeat until you pop the achievement. It's quicker because once the time limit is complete and you have two laps remaining, instead of it taking 2 minutes per lap it's only 9 seconds per lap. So it's 3 minutes plus roughly 18 seconds per win.