For example i want to make a game that is called "scrolls" but im not sure if this word isnt trademarked already (i know it is, notch probably has it), can and where i could find this out:?
Notch was sued by Bethesda because of the similarity to 'The Elderscrolls: _________' series of games; which is an excellent example of, "Is it similar to someone else's trademarks?"
Before you bash Bethesda too much, companies are required to defend their trademarks or they lose ownership of them. Same with Nintendo suing people for Mario or Pokemon games - the more people that make games without permission and without Nintendo taking action, the less control and legal ownership Nintendo has over their own property.
Another thing, lets say that the trademark exist, lets say the word is "Lazy potatoes" (just an example), i want to use this for a pc game, but i find out that this is already a trademark but it is used by some chips (food) manufacturer, so its just some stupid food, it doesnt have anything to do with games. Could i use it for a game? I gues what im asking is, if the trademarks are somehow tied to the "field" in which the owners has bussines (law, finance, entertainment, food, drugs, car, real estate etc...)?
Yes, to an extent. There can theoretically be multiple "Super Cool _______" companies ("Super Cool Drycleaners", "Super cool motel", "Super cool internet server provider!", "Bob's supercool mail delivery service"), because those are common english words that are commonly put together in that manner but are all in different industries.
Even so, companies don't need to be actually in violation to sue each other. I can sue someone for breathing. That doesn't mean I'd win, but it'd still be a huge nuisance for the person being sued.
When filing the paperwork to create their company, the two college student founders of Google accidentally misspelled the word they were trying to spell (Googol). They found out later that this was actually beneficial to them, because by (accidentally) creating a unique word, or unique spelling, it strengthened their trademark. Nobody can use 'Google' for anything, regardless of what industry. You can't make Google Burgers, for example, because 'google' wasn't a word that existed until Google was founded.
Had they named themselves Googol, they would've still had control over that name in the software industry, and related industries, but some bank could've created a "Googol saving account", as long as they weren't intentionally trying to capitalize off of Googol Software's popularity.
As an example of a company that doesn't have a unique name, Apple Software uses 'Apple' as it's trademark... but 'Apple' is a common english word. Apple Software only has control of that trademark in the software and computer hardware industry.
Apple Corps (the Beatle's recording studio) has control of it in the music industry, so when Apple Software got into the music business with iPods and iTunes, Apple Corps sued Apple Computer, and it was a long, expensive, messy legal battle. Had Apple Software chose a more original name for their company when founding it, they could've saved themselves hundreds of millions of dollars in settlements and lawyer costs over the years.
There are also apple grocery stores - in Kansas City, there's a Cosentino's Apple Market chain of grocery stores with at least three branches. Apple Software, despite now having retail stores for their computer products, can't do a thing about that. Try making a Cosentino's Google Market grocery store, however, and you'd get sued into smithereens, because 'Google' is a unique word with unique spelling.
Even things like the Macintosh name? Macintosh is a popular and common name for a specific type of apple fruit. Apple's marketing team probably felt they were being clever with the name. Apple's legal team probably groaned. Nothing is preventing anyone from creating a Macintosh Airlines, or Apple Jets (though they may have trouble naming an airport 'Apple' 
)
Obligatory: I am not a lawyer, consult a real lawyer before making important long-lasting business decisions such as naming your company or flagship products.
