First: air bags. These are cheap and easy to install. They work great.
Air Lift 1000 Air Suspension Kit 60804 https://www.amazon.com/dp/B098BLD5B1/ref=cm_sw_r_apan_glt_i_FDYQTQ0E8Y2FDFV3C95F
Second: ditch the trailer. Switch to a tow dolly. You will need to drop the driveshaft on the BMW. Put a gallon zip lock bag over the transmission tail housing and duct tape it up. Like someone else mentioned, you will be pulling a lot less weight.
Safe travels!
These were a game-changer in my 4Runner that I use for towing.