Do I have to boil canned food, specially tuna can, in water for twenty minutes? I think it's necessary to prevent food poisoning by botulism. However, currently that I am in Europe, I have not seen a written passage on tuna can to advise people to boil the can before consumption, or did I miss to see such a thing?
No, you should not need to boil your canned food. Most canned foods have already been heated to boiling — or higher — temperatures to kill all microbes as part of the canning process. Seafood is heated to temperatures even higher than boiling and canned under pressure.
Canned food is, by definition, sterilized and hermetically sealed so unless you believe the seal on the can is compromised, canned food is safe to eat as-is.
If you don't trust that it was properly canned, or you think the can's seal is broken, then simply don't eat it, boiled or otherwise.
It's interesting to note that canned food over 100 years old has been opened and — despite losing its flavor and nutritional value — deemed safe to eat.
Commercially canned food (at least in reasonably wealthy countries, which I think would include at least all of the EU) is safe to eat straight out of the can. Provided the can is undamaged, of course. Damaged, bulging, etc. cans should be discarded.
You didn't say what country in specific you're in, but your country's health, food safety, etc. department should have specific guidelines to your country, if any are needed.
You definitely need to boil the can in order to prevent yourself from possible poisoning. It's not about trust or truth it's about your own safety.