Hi, i have a little problem, i fill some greather soul gems with petty souls and i want to know if i can refill the gem with a greather soul or they are just ruined? u.u

They are ruined, if you would have had petty soul gems with you they would have filled those first

Nope. You only get to fill them once. After that, you can either sell them or use them to charge or enchant something. I find it best to carry an asst of sizes cuz what's killed will go into the smallest one it will fit in first.

Actually, there is a bug (on PC anyway) where if you drop a full soulgem on the ground, it can empty out.
I was able to exploit this to "repair" some greater and grand gems I had that had lesser souls in them.
Souls are cheap, gems aren't.