The constitution of Namibia allows for freedom on religion and the country is a secular state. It is thought that around 90% of Namibians are Christian, and a surprisingly large number actively practice there religion with regular church attendance. The largest Christian group is the Lutheran Church which grew out of the work of the Finnish Evangelical Lutheran Mission. Next largest are Roman Catholics, while most other Christian denominations can also be found.
Other religions that are practiced in the country include Judaism, Islam, Buddhism, and the Baha'i Faith (and there is even a rumour that their may be one atheist lurking somewhere in the country!)
People tend to take their religion very seriously, and if you are not looking for a long lecture and an attempt to convert you to the joy's of Christianity, it is probably a subject best avoided. There are several lodges around Namibia which place an emphasis on Christianity, they can generally be easily spotted as their name has a religious angle e.g. God is Great Lodge.
On a serious note whatever your religious persuasion you will be warmly welcomed in Namibia.
In religion and politics, people's beliefs and convictions are in almost every case gotten at second hand, and without examination. Mark Twain