Shalom, Rabbi! Perhaps this is an odd question but is there any reason why I should not study more than one parshah at a time? We will read parshat Korach this Shabbos but can I also review Bereishis? Must I focus my limmud solely on this weeks portion?

Thank you for your important question, There is no problem to study next week's parsha. I'll just mention two comments: 1. Shnaim mikra can be read only one week ahead from shabbos afternoon a week early. 2. I would focus mainly on the weekly portion so you can discuss the parsha with others. Additionally there are sources that the weekly portion relates to every Jew on that week. The Lubavicher rebbe mentions this many times. All the best!