I need to know the best course after B.arch.?

A master's degree in architecture or an MBA in construction management is both viable options. Here are some programs to consider if you want to apply for a master's degree and want to know your options. Here is a list of courses that you can target:

Master's in architecture
M.Arch. in Conservation and Restoration
M.Arch in Architectural History and Theory
M.Arch. in Landscape Design
Masters in Urban Planning
Masters in Urban Design
Master in Urban Housing
Countries worldwide want to own the tallest and most complex structures but also need sustainable designs for smart cities and townships. This has increased the demand for highly skilled professionals in the field. To fill the void, universities worldwide have begun offering comprehensive programs to produce leaders in architecture. The following are some of the top schools that offer M Arch degrees:

Massachusetts Institute of Technology (MIT)
Harvard University
The University of California, Berkeley (UCB)
University College London
Delft University of Technology
ETH Zurich 
National University of Singapore (NUS)
Tsinghua University
The University of Melbourne
RMIT University
University of Hong Kong (HKU)
Although the eligibility criteria for the program vary by institution, if you plan to study abroad at the top architecture schools, the standard eligibility criteria would require a Bachelor of Architecture degree. In addition to the academic requirements, you must have a valid GRE score. Furthermore, because the courses are taught in English, you will be required to demonstrate your proficiency in the language by taking one of the tests such as IELTS, TOEFL, or PTE. In addition, you will be required to submit university transcripts, letters of recommendation (LOR), a statement of purpose (SOP), an updated CV, and other documents. Although not required, some universities may require a strong portfolio and work experience. If you have any further questions just ask me.