Learning the combat mechanics isn't a easy task for some people, which is normal.
The only way you can learn how to do anything in life is by practising it over and over again.
I'd recommend you just to be a little more patient about this, because it takes some time to master it.
It may take months, or even longer, but it's fairly easy and simple if you practise against different opponents while playing Duels, or 1.8/1.9 FFA.
Again, it won't happen instantly, or for a day or two, but after a longer period of time you will feel the difference ;)