Hi cmitt, and welcome!
1.combat weapons have only heavy , arcane etc properties. Can someone make more prorerties for them as ''steel'' : -1 modifier for d4 roll 4 for example ''gold'' : -2 on armour for roll 5,6 on d6 with corresponding cost or is it too much
Combat weapons in the 2011 Edition can have any weapon property that is marked as "Combat Weapons Only" or that is
not marked as "Shooting Weapons Only". This gives a wide variety of possibilities for these weapons.
Not quite sure what it is you mean by giving a weapon "steel", etc. Are you after an ability to defeat armour and shields easier? If that's the case just use AP-B, AP-H or AP-X. These give different bonuses to busting armour depending on the armour they are up against. There's no real need to give further randomised bonuses as the standard ones are already random, and yes, it may possibly be too much to remember in gameplay.
I am considering a bunch of options for later supplements, which are already in the works. I think that I can see what you are hinting at here, and such weapons aren't properly covered by the core rules. They may well be covered by what I am planning though. Stay tuned.
Heavy (which is soon to be obsolete as a property) equates roughly to AP-B. In upcoming versions you'll find this system has been tidied up a bit, and all weapons have all properties available to them.
2.how many properties of the model or weapon can occur in a turn?
If a weapon has a property, it is active unless that properties rules say otherwise. For example, an unstably invisible model may not be invisible all the time; an unreliable weapon won't be unusable unless it rolls a one; and so on.
So I guess the short answer is all of them, unless the rules say one or more are not.