WARNING: This page is about a different car, the 2018 BMW 340i, 2017 BMW 340i, and 2016 BMW 340i. However, it is still accessible from the selected car via links, so may be relevant.
Install the oil-level sensor (3).
Tighten nuts (2).
TIGHTENING TORQUES SPECIFICATION
Oil-level sensor to oil sump
M6
Joining torque
2 Nm
tightening torque
8.5 Nm
Connect the connector (1), it should lock audibly.