Which places or regions are suitable for mountain trekking in Namibia for travelers for 10 days?

Namibia, a country in southwestern Africa, is home to various wildlife, especially a number of significant cheetah population. Now Day 1 starts with reaching Windhoek (capital of Namibia) where we travel north toward Okahandja (famous for wood carving market) and continuing through farmland to Okonjima (home of the Africat Foundation - a specialist conservation concern). Day 2 begins with leaving Okonjima - Namutoni, Etosha National Park (a safari which is the best place to spot black rhinos), and a hike of 2 hours. Day 3 will be traveling from the East Etosha region - Okaukuejo and Day 4 to Grootberg. Day 5 begins with traveling Grootberg area - Twyfelfontein and on Day 6 and 7 is to reach to Swakopmund and to visit German colonial architecture in coastal regions of Swakopmund. Day 8-10 is to travel to the dessert spots of Swakopmund - Sesriem and hike for about 3 hours on those sand dunes with locals and watch and climb the infamous Sossusvlei dune belts also known as "Namib sand sea".