Any degree from Sikkim Manipal University-Distance Education is completely valid if you want to apply for further education in German universities. In fact, your degree is valid for applying to any foreign university. The courses offered by SMU-DE are certified and approved by the University Grants Commission, in other words, they are recognized by the government. So, you should not face any problem when it comes to applying to foreign universities.
Generally speaking, most of the foreign universities where some of my friends had applied required the candidate to have completed a certain degree from a recognized institution.
At the same time, you must carefully read the admission policy of the college of your choice. As you have not mentioned any particular college in your question, ensure that you satisfy the different criteria specified for the college or university you wish to join.
A particular college may have different requirements for admission in two different courses. Moreover, two different colleges within the same university can also have some variations when it comes to eligibility. So I would advise you to ensure that you look at all these points closely before submitting your application.