I`m 13 years old and i have to do some projects to school.
Is there possibitity of any free student edition of photoshop or free trial?
S&T editions do not come "free". If you are eligible, you can buy it at a discount.
The trial will run "free" for 30 days and that's it. Download it from the product page. Otherwise there's plenty of free or affordable tools out there like GIMP, PDPaint, ArtRage and others that no doubt will do the trick for many things.