Look first for forcing moves.
How to solve chess combinations ?

It helps to know the basic tactical motifs and how they work: http://chessskill.blogspot.com.es/2012/04/tactical-motifs-list.html

It helps to know the basic tactical motifs and how they work: http://chessskill.blogspot.com.es/2012/04/tactical-motifs-list.html
Pulpofeira you can be sure i know the basic tactical motifs and they give me no help

1. Rxf6 and then Qh7+ and then Qxf7#
You cant capture f7, there is bishop between h7 and f7, and it silly to consider black will capture with bishop

I saw that too, but be careful.
calculating that much gives nothing, i calculated around 8 moves deep and still couldnt find the win, and combination is combination it has tactical nature it needs to be found till mate or material advantage, if i only had to find first 1-2 moves and intuitively decide its ok before seeing the rest, i would solve every combination in 5 seconds. But working on hours on this with no result yet.

Any help from a player could help, may be titled players can you give me an advice to how to solve them ?

Note that his tactic rating is 2100, so he is not that stupid.
I didn't say that. Care to take a look at his original post?

Well if his tactic rating is 2100 he ofcourse will easily do these you have posted
As usual here, you only care about numbers. What I see is a guy who states it took him 10 hours to solve (badly) 9 chess combinations, and that knowing about tactical motifs doesn't work for him. Maybe he's just trolling, who knows.
My question is clear, it is always said that to improve your calculation and tactical vision solve lots of combinations, but how to solve them.
I started solving encyclopedia of chess combinations today, in 10 hours of work i solved 9 and only 2 of them were correct, another 2 of them were partial.