Train from Freiburg, 2 per hour to Titisee station, 1 per hour to Neustadt.
Walk or use the local buses. Or hire a bike.
Walking is the principal activity in summer, with a network of well marked routes. Usually you will find an inn somewhere along the route!
Skiing takes over in winter, as long as there is enough snow.
A number of reasonably priced restaurants in Titisee serving traditional Black Forest fare. Also a Chinese restaurant!