as for character: thursday threads usually announce what game will be played, but usually it’s going to be pregens or quickly made characters at the spot especially as sometimes it’s more rare or unique games
friday is D&D 5E with our own ruleset (which can be found here) based on Adventurers League, for those you can either bring a prepared character (for first time you usually will need to start at level 1, details can be found in the rules) or come a bit early and create one with some of the people that are already there and can help
on thursdays i would assume the guys at Spielbar won’t be happy if you bring your own stuff (for special occassions it usually is possible for stuff they don’t sell like cakes if you call ahead) on friday some minor snacks are ok with Cafe 1070, but it still is a business so drinks should be bought there if at all possible