SRS malfunction could be the seatbelt buckle related. My coworker has a 09, E550 and had this sign few weeks ago. He went to dealer to replace the seat belt assembly under warranty.As the SRS is digitally connected with your seat belt. Belt assembly replaced and ECU cleared. I am not expert but maybe a small sensor not responding.
Congrats anyway. You are millionaire in Toman..
The thing on the boot is called rear lip spoiler .. 