Could you help me with a proper use of articles?
A. I was at a Madonna concert in London last week.
B. I was at a Madonna's concert in London last week.
C. I was at Madonna concert in London last week.
D. I was at a Madonna's concert in London last week.
What about names and surnames?
E. I was at an Ewa Farna concert in London last week.
F. I was at an Ewa Farna's concert in London last week.
G. I was at Ewa Farna concert in London last week.
H. I was at Ewa Farna's concert in London last week.
And finally what about bands, especially in plural or in foreign language?
Wilki in English means (Wolves)
I. I was at a Wilki concert in London last week.
J. I was at Wilki concert in London last week.
K. I was at Wilki's concert in London last week.
L. I was at a Scorpions concert in London last week.
M. I was at Scorpions concert in London last week.
N. I was at Scorpions' concert in London last week.
O. I was at Scorpions's concert in London last week.
Which versions are correct? What should I use?
Could you provide a good explanation?