something to know, when you are performing the combo.. you need to press the next key when you previous key hit the enemy...
following your example : Kick > when it touch the enemy > press the next key ( punch ).> when the punch hit the enemy > follow with the next key ( kick ) .. the timing is simple as that.
The combat are not really hard, you just need to use the "life regain combo" when you see your life down, and use power combo for break their defense.. the camera is horribly bad placed sometimes.
Then when you fight invisible enemy, its more a question of timing for active the light by active interruptors in the environnement with your weapon for see themoutside the lighting zone, you dont see them, and cant hit them otherwise, or you can use the appropriate "sense" who let you see them during a certain time....
When you see a red " ! " over the enemy.. just use the jump. ( you can continue your combo after have jump, it dont stop the combo ).. so fight are a bit strange.. basically you start your combo, jump over them, then continue your combo, jump, etc etc.. a bit repetitive, and if write like that is simple, continue a combo after interrupt them, lead offtly to dont press the right key then, and stop it.. with some type of enemy and the need of use the environnement, you need to be really fast .. When the enemy are on the wall, just use your weapon for make them fall, then you can attack them.
Its again a nice idea they have got in the fight, to use the environnement, the light, the shadow etc .. this game is full of nice idea.. but sadly on the realisation, its a bit of miss and hit.
The menu for create the combo, is just really bad, absolutely not clear.