Why does parshas Bamidbar come before Shavuos? (short)

The Chidushei HaRim notes that the sedra of Bamidbar generally falls very close to Shavuos. What is the message of this juxtaposition? He answers that parshas Bamidbar is all about Bnei Yisrael’s formations in how they camped and traveled. Each tribe, family, and person had their own place within Bnei Yisrael. This shows that each person in life has their own unique place and role within the Jewish People. [And just like the Mishkan was in the centre of the formation, so is avodas HaShem the central aim in our roles] Realising that each person has their own unique place/role fosters unity and working together as a team for the common goal. In short, the message of Bamidbar is achdus by realising that every Jew has their unique role. And this leads up perfectly to Shavuos, for just like when we got the Torah we were unified ‘like one man with one heart’ (Rashi), so too to receive the Torah on Shavuos each year afresh we are to first learn the lesson of unity.