Is reading newspaper sufficient for covering current affairs or monthly magazine is must?
Newspaper is not only necessary, but also a sufficient source to prepare for the current affairs; however, monthly magazines can also be used as a supplementary source to get additional details, background and different perspectives on the news that you have read, something, which a newspaper may or may not provide.
Thus, you may access a few magazines and check, if provides something in addition to what you already have covered from newspaper or not and then decide, if it does, a magazine could be helpful for you. But definitely it can’t be a substitute for reading newspapers and can at best be a supplementary source.
In short, don’t use magazine as a collection of news, but as perspective on them.