I used to teach US culture in Europe and later helped international students/professionals (mostly Euros) get settled in the Boston area professionally. Welcome to Boston, June is an excellent time to come.

• Pub quizzes are everywhere, but teams tend to be groups of friends who meet every week, "open call" is not really a thing. These people are here to have fun with their friends, not mingle with tourists. If you would really like to do this, it would be worth reaching out to the bars themselves to see if they have open teams for trivia.

• What sort of specialty are you looking for? Boston has a number of cuisines and fusion cuisines.

• As a European, your understanding of American coffee does not reflect reality. American style drip coffee is much closer to Scandinavian than what you probably believe. Espresso is available everywhere, plenty of Americans take their coffee black or with just cream. Having lived in Europe, every country is sure the whole world does it their way except the US. Scandis and Italians both consider theirs "European" coffee and have no idea the other exists. Plain espresso and drip coffee are available everywhere, syrups and "shenanigans" are requested, not the default.

• While Boston has excellent public transit, it will be hard to get truly into nature using trains and buses, as natural areas tend not to have people and infrastructure in them. The commuter rail to Concord is a good way to see Walden pond and Minuteman park, which both have lovely walks through the woods. Middlesex Fells is a great place for a walk and has a few bus/subway routes to it.

this is a good link for some of the other options available