Welcome, Ausfahrt! I'll start you off.
Beneath the combination oil/water pump at the front of the engine is a weep hole. If that hole is moist with either oil or coolant you will likely have a seal replacement job ahead of you if it starts to drip more than occasionally and you have a low tolerance for imperfection. Replacement is an exacting procedure that requires patience and OEM seals and other parts to complete. Many here have done it—more than once if they weren't patient enough the first time.
The green arrow indicates the oil filter cover on the oil sump; the red arrow indicates the weep hole.
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The forward lower part of the transmission case has a weep hole. If engine oil is discovered there the most likely sources are the rear main output shaft seal or the output shaft O-ring, or both. Replacement of those is covered in many threads here and in Clymers, Haynes and the BMW workshop manual downloadable here. If transmission oil is leaking from the hole, you'll eventually need to replace a transmission seal on the front of the transmission. Red arrow is at the weep hole; green arrow is at the sump. Part of the center stand is seen.
If oil has leaked onto the pavement from the rear of the transmission swing arm housing, the clutch boot has been torn and will require replacement or the clutch arm is not contacting the clutch piston sufficiently and will need adjustment.You can ask when the rear drive pinion splines were lubed and what lube was used, and when the transmission input shaft splines were lubed and what lube was used. If no information is forthcoming, you'll need to do both those tasks. There's plenty of help here and in Chris Harris's videos. These shafts are the Achille's heel of two-valve Bricks. Regular maintenance is essential for their wellbeing.More suggestions will undoubtedly be posted.