I also want to point out that the Pre Season SX Track is extremely unforgiving, this coming from someone with over 1K hours. I would recommend trying some easier SX tracks because as Teeds mentioned, SX is hard IRL and that much more in MXB. However, after investing some serious grind time into SX it personally has become very addicting. You will improve at the game much quicker because SX requires much more precise bike and rider lean control, along with learning how to recover when you slightly case or OJ sections. My all-time favorite SX track that I still load up at least once a week is the 2020 race edition of St. Louis by Ruubs. Just an outstanding track that offers everything you'll ever find on an SX layout. Get to the point where you can run consistent laps on this track and then you'll be ready to move up to slightly more difficult tracks.
2020 St. Louis Race Edition
2020 St. Louis Race Edition