Aspiring to pursue a master's in a Natural Sciences in Germany. What are my chances?

my_qualifications: BSc in PMCS 3 years from a local college affiliated to a state university with 65% (2.7 german grade).

I want to pursue a MSc either in Mathematical Physics or an interdisciplinary subject like Computational Sciences.

IELTS : 6.5

APS : Acquired

I went to a reputed consultant who told me that your percentage is on the lower side and there is competition, also he said that admission to a public university will is very challenging and that I should try for Data Science in a private university.

I want to know objectively from applicants or anyone who knows about all this, what are my chances realistically?

Should I go for a private university where fees are 15-20K Euros for the entire duration of the course?

I have also read and heard from people that a three year degree poses a serious risk of rejection, is this true?