Weak in middlegames and positional understanding

I am battling in the middlegame.How should I improve from 1350 to 1600 in a years time?

Chess Secrets: the Giants of Strategy by Neil Mcdonald is where I learned my middle games and positional chess. Study it and you may even learn more than me. Better than "My System".

Thx Mandy

I have found the books by Jeremy Silman very helpful. A bit exspensive, though.

How was Silman's Endgame book?

Yasser Seirawan was a Master Strategist, all his Youtube videos are worth watching.

Personally would not recommend Silman's work.  I'd recommend two books on the endgame to get you to where you need to be, minimalist style:

1.  100 Endgames You Must Know by de la Villa, and

2.  Endgame Strategy by Shereshevsky.  

First one will give you the basics on theoretical positions that are important, second one will give you understanding of how to play the endgame.