You Do Need power plug adapter while traveling from Germany to Eritrea.

Here is Why You Need An Adapter

The outlet and plug type used in Eritrea are C and L and in Germany are C and F. This is how they look like.

Germany

In Germany, outlets of type C and F are in use.

Type C

Type F

Eritrea

In Eritrea, outlets of type C and L are in use.

Type C

Type L