Please help me to improve my games...

I gather that you have no complete Heisman sentence to back up your interpretation of Heisman.

I said nothing about spending "a month of Caro-Kann book". GM Artur Yusupov used the idea of mixing up one's areas of study - learning a little bit at a time for an area of study.

"... This book is the first volume in a series of manuals designed for players who are building the foundations of their chess knowledge. The reader will receive the necessary basic knowledge in six areas of the game - tactcs, positional play, strategy, the calculation of variations, the opening and the endgame. ... To make the book entertaining and varied, I have mixed up these different areas, ..." - GM Artur Yusupov (2010)

"... A remark like 'games are rarely decided in the opening' does not really do justice to the issue. ... even if an initial opening advantage gets spoiled by subsequent mistakes, this doesn't render it meaningless. In the long run, having the advantage out of the opening will bring you better results. Maybe this warning against the study of openings especially focuses on 'merely learning moves'. But almost all opening books and DVD's give ample attention to general plans and developing schemes, typical tactics, whole games, and so on. ..." - IM Willy Hendriks (2012)

"... You need help finding an appropriate middle-game plan that suits the position. ..." - blueemu (to ianyl18) (~9 hours ago)

Again - my advice is my own opinion, from my own experience. That experience is that when I follow universal principles, no theory, against OTB 1400-1600s, I've always gotten out of the opening fine, often with an edge.

When the OP gets to 1800 OTB, my *personal opinion* will be that he can, should in fact start studying specific openings. I learned 90% of my opening theory between 1800 and 1900 rating. 

I was at the OP's level a lot more recently than these masters, and again, this is my *personal* approach to improvement, which in part agrees with Heisman. 

By now, the OP can decide what he wants to do, so I won't argue anymore. 

"It is important for club players to build up a suitable opening repertoire." - GM Artur Yusupov (2010)
In one of his books about an opening, GM Nigel Davies wrote (2005), "The way I suggest you study this book is to play through the main games once, relatively quickly, and then start playing the variation in actual games. Playing an opening in real games is of vital importance - without this kind of live practice it is impossible to get a 'feel' for the kind of game it leads to. There is time enough later for involvement with the details, after playing your games it is good to look up the line."
https://www.chess.com/article/view/3-ways-to-learn-new-openings

https://www.chess.com/article/view/how-to-understand-openings

If you insist - but the OP has now enough info to decide what he wants to do. 

I don't "insist". I offer ideas - alternatives to "from my own experience" thinking. For opening principles, an alternative to Watson is Discovering Chess Openings by GM John Emms (2006).
https://web.archive.org/web/20140627114655/http://www.chesscafe.com/text/hansen91.pdf