hTTi

This PDF is explaining me if the the country where the Bond is emitted will tax the Zins matured.
https://www.bzst.de/SharedDocs/Download ... onFile&v=3

What I can't find is the same information/table but related to the capital gain on the bond. I mean the difference from the 100 full nominal value when the bond expires and the price I have bought it. I am not considering the case of trading bonds, i bring them to expiration usually.

Can someone please point me in the right direction with some german keywords to use with google ?

You always have to tax both the interest and the gain in Germany.

The other country does not charge tax on the gain, your country of residence, Germany, has the taxation rights on it (except a few countries that charge an "exit tax" when you move away from them - but that wasn't what you were asking, you want to invest in non-German bonds while already being a German resident).

All that document does is tell you the source tax that the other country charges.
You still have declare the interest in your German tax return and then that German tax will be reduced by the non-German source tax that you paid on the interest.