If you have a name / logo in mind which you like to turn into a trade mark, you need to put it in a kind of “category” let’s say Computer Games / Software if you turn your logo and name into a trademark in the “category” Computer Games… Your brand is just protected for this special “category” “Computer Games”… So someone else could come arroud and take the same name but make a Soft drink from it… The most smaller companys protect they’re names only in the category which they are using, for example… food or fashion or whatever, however you will find sometimes bigger companys like Cocal Cola which take demand of multiple “Categorys” so they protect they’re names in almost every possible “category”… You have to keep in mind, that every “category” costs extra and if you like to protect your name and logo on the whole world you have to pay for it… and we are talking here about big money…
To make it short, just because a name exists on the market it doesn’t mean you can’t use it anymore… it depends what this company / name is doing and in which “category” they have protected they’re name. However they are even names you can’t protect. Let’s say you wan to open a game studio called “Amsterdam Game Stuidos” you can’t protect any of this 3 words, cause they are property of the community… but you can still use it in combination with a logo and protect them this way…
It’s a long subject, my suggestion is take a lawyer which is specialized in Trademarks, cause he will do also the research for you… and he will tell you if you can use this name for your project…