Goethe University is one of the best universities to come for Erasmus. If you have a basic German education, Goethe University offers free German education for a month (just a month before semester start) and if you wish, you can continue studying German during the semester and it counts 9 credits. The official language in university is German, but most of the courses in economics and business is in English and almost everyone in the campus speaks English. It is very important that you apply for your student card as soon as you go to the university because you will need that card in the library, dining hall and transportation. You will deposit 300 Euros to the university account by transferring from your home country (it takes 2-3 weeks) or you can do it in Germany (it takes 5-6 days), then after applying, the university will give you your card within 2 weeks. With this card you can use the U-bahn, S-bahn and Regional Bahn trains unlimitedly during the semester around Hessen. With this card you can also use the lockers in each building in the school to leave you books and coats, you can install money into it and use it in Studierenwerk(student office) cafés and dining halls.
Goethe campus is very regular and it is one of the most beautiful campuses in Germany. In the university you can do administrative work in psychology building, you can go to the Amphitheater lectures in Hörsaal, you can eat your meal at the Mensa or other mensa (cafes) around campus. Behind the University’s EVG building, there is a wooden building called Raum der Stille (Quiet Room) where you can practice your worship of any religion or kind, or stop by just to sit calmly (Muslim students use it to practice salah, there is also wudu place).
Course selection in Goethe takes place as exam registration; you can apply by preparing a form with the courses you want to attend until the middle of the semester. There is no restriction on the credit or lecture count, you can have as many. Most of the courses are 100% final oriented, final grade determines your whole grade. Lectures in terms difficulty, cannot be said easy or hard, they are at medium level. Half of my classes were Master course because I went to winter semester so it was harder for me. So you can prefer summer semester. A good thing about the university is that the slides of all the courses are on the system OLAT you are enrolled with, and even some of the lessons are recorded as videos. Being a student in Goethe is more compelling for that reason, but still the university is often crowded, especially libraries in Rewi (Law and Economy) and Psychology buildings are often crowded. As a result, you can pass your some of your courses with slides and videos, even if you do not go to lectures. But my suggestion would be going to the lectures to actually learn from good academics. As a note, the best grade for the German system is 1, then it goes as 1.3, 1.7,2, 2.3, 2.7, 3, 3.3, 3.7,4 and the last passing grade 4, below 4 as in 4.3, 4.7, 5 you fail the course.