Berlin is totally central....:)
(and secretly the real capital anyhow)
It is not a secret, BB :) Warsaw is a better kept secret: besides a few people nobody else knows that it is a center ;)
looks like a heart
Indeed, there is resemblance, but as you know the heart is not in the center :) The center would be a bit further to the right (thus, to the west), which gives Germany another point.
What about the Oder? Nice natural curve for a center and will satisfy the two countries.
But to be true to the measurements as midpoints of the Europe's extreme points Belarus would have the center point:
The geographical midpoint equidistant to these extreme points (if 66° 11′ 57″ E is used as easternmost point) is at 53°34′01.5″N 28°20′57.2″E / 53.567083°N 28.349222°E / 53.567083; 28.349222, 15 km north east of Marina Gorka, Belarus. The centre could be 1° to the east.
en.wikipedia.org/wiki/Extreme_points_of_Europe