Denis Stoikovski :
That explained me a lot thanks! But one more thing how do i clean it? And if i scratch the chip somehow will be this fatal?
Denatured or isopropyl alcohol works fine. you can use it on a Q-tip or a piece of paper towel. With the CPU cooler there is really nothing to worry about when cleaning but with the CPU you want to be more careful. On the side without contacts (top side) where the paste is the paper towel or Q-tip won't scratch it so there is really nothing to worry about but you have to be care full not to touch the bottom side (where the contacts are). If you do happen to touch it don't freak out it's just best not to.
As far as scratching it (the top side) goes that wouldn't be fatal, but a scratch creates high and low spots and you want to keep the top a flat as possible for the best cooling. Some people lap (lap or lapping is basically polishing them to be as smooth and flat as possible) their cpu's and heatsinks and you could do this to take out a scratch but even if I had a small scratch in my CPU I wouldn't worry too much.
When you apply the new paste put a small blob in the middle. Some say about the size of a pea and some say the size of a grain of rice. I usually shoot for the middle of those two.
Then there are two techniques for what to do next. Some spread the blob evenly across the top of the CPU with something flat like a credit card and some just press the cooler on which also spreads the blob. I have tried both and either is OK.
When you spread it yourself you ensure complete coverage, but you may have a greater chance of getting an air pocket. When you press the blob out the coverage in the corners may be slightly lacking and although both ways have worked fine for me, I usually use the spread method.
Also if your cpu is more rectangular than square the paste should be applied in more of a line than a blob.
Your CPU should be in your board and locked in place before you attach the coolers heatsink.
This is a good video for cleaning. The coffee filters are a good idea and the goo gone is also a good step if you have anything tough to remove. Although I have to say I've never had to use it.
For applying the paste, type this: "apply thermal paste to cpu" into Google and select videos. there is a ton of them.