I am a 1100 rated player.In rapid and blitz games I beated 1600 players this proves that my intution is good but at classical matches I can't even handle a 1300 player.I am a positional player as I just need a moderate advantage .But I am weak in long term calculation as I can't judge my opponent's move so kindly tell measures improve my calculation
You could make your question more specific, giving examples of when and what type of moves you fail to take into account. Anyway, I am 2050 and suffer from the same, so, it is a relevant concern for players of all levels! Start with distinguishing forcing moves, from non-forcing ones. Basically, unless you've given a check, your opponent can, in theory, play any move they wish. Thus, look for as many possibilities as you can afford the time for. My own problem: I tend to fool myself into believing that my opponent and I together are trying to produce a stunning, beautiful game! As if he/she will not ruin my beautiful strategy I have in mind, and they will help me carry it out!! "I attack this pawn and of course they will defend it..." And then I got the shocking response that sends chills down my spine, waking me up from my dream :))
Do not ASSUME that by default your opponent will respond in the way you think they should/must. Try to look for all possibilities on their behalf. Look for the strongest they can play.
Not an answer for all situations, but let me share with you something that helped me in some specific situations. One big mistake I was making at one stage was to look at my opponents move, deem quickly that it looked innocuous, dismiss it, and continue with whatever attack plan I had previously formulated.
The mistake I made was to treat seemingly innocuous moves with less caution than other moves which presented an immediate threat. After a while, I learned that seemingly innocuous moves require MORE caution. If your opponent has made a move which doesn't immediately seem to improve her position, you are probably missing something. Sure, sometimes it is just a poor player or a bad move. But in my experience, it is more likely that they are seeing something you are not.
So when your opponent makes such a move, alarm bells should be ringing. Where could that piece move to next? Think about the best position for that piece, does this move help them get there? What rows or columns does it open up for their rooks? What diagonals does it open up for their bishops? These are all questions you need to ask when such a move is made.
I good youtube site is maintained by ChessDiagnostic: https://www.youtube.com/channel/UCBnaQU92Z4qaNsIwkxV0GNA/videos
He has a series of lectures. Look at: https://www.youtube.com/watch?v=fzGKPxJ5NYI&t=1003s