Founded in 2015, Sprachinstitute Berlin is a boutique language school offering intensive, evening or one on one German courses from beginners to advanced. They offer a personalised experience with small class sizes and high quality native speaking teachers.  Both founders have extensive experience managing large language schools and have created a school with a definite focus on the individual student.
In addition to their intensive courses they also offer Grammer, Conversation or Phonetic classes which can be taken as add-on options or stand alone modules if you require more help in a particular language area.
A four week intensive course comprising 20 teaching hours per week costs a very reasonable 298€ particularly considering the maximum class size of 8 students.