The calculated distance (air line) between Bonn and Mittegroßefehn is approximately 185 miles respectively 297 kilometers.
By car or train, the actual journey to Mittegroßefehn is certainly longer, as only the direct route (as the crow flies) between Bonn and Mittegroßefehn has been calculated here.
Air line (approximately)
297 kilometers
160 nautical miles