My car showed a certain liquid which was like water with a certain amount of oil which was leaking, so will it continuously show this leak if I drive it more 20 miles having it tightly fastened?
It sounds like your M3 is leaking coolant - that would explain the "clear, but slippery" liquid - although it is unclear from where. Rather than risk engine overheat from driving it further, I would recommend having YourMechanic diagnose this issue, provide an accurate assessment of the leak firsthand, and estimate the cost of repairs. YourMechanic can dispatch a mobile, professional mechanic to your location to service your car. This is a wonderful engine to ruin over an overheating event due to no coolant!