You Do Need power plug adapter while traveling from Switzerland to Namibia.

Here is Why You Need An Adapter

The outlet and plug type used in Namibia are D and M and in Switzerland are C and J. This is how they look like.

Switzerland

In Switzerland, outlets of type C and J are in use.

Type C

Type J

Namibia

In Namibia, outlets of type D and M are in use.

Type D

Type M