Is it possible? Yes
is it easy? No
According to German laws, Students can work 20 hours per week and 120 full or 240 half days in a year. So the average basic salary is around 9 to 11 Euro per hour. The minimum salary is somewhere between 9 & 10 € (In 2020 it’s 9.35€) per hour, you can not get below this amount if you are working legally. This is the general criteria you will have to follow during your part-time work. Per day maximum working hour is 8, it can go till 10 but more than that is not allowed for anyone not even for German employee. Two extra hours is also complex, some say it will be counted as extra day so you may lose 1 day from your 120 days by working 2 hours extra, but I am not sure on this topic. Not following these rules might get you a penalty from German authorities, only in the extreme conditions like working more than 150 Full days or more.
Now reality is it’s impossible to utilize those 120 days if your primary goal is education and also you want to score well in your exams, but you can start with the initial blocked amount in your bank account and try to maintain this balance around 4–5000 €, here you can work during semester break full time and earn some good money and during semester just earn to fulfil major expense such as rent and insurance, you can do a mini job (450 €). This will be the optimum approach as per my advice.
Getting a good job without good german skills is not an easy task, you will end up doing a labour job where language skills are not required. Another factor is the city where you live, bigger cities offer more job opportunities. Some people can also find the job at the university itself, but not everyone can find it, as the numbers of such jobs are also limited.
Another thing I would like to explain is the greediness of earning money. As once you become greedy, you will do more and more part-time job, as once you start with any kind of job, the job provider will always have a shortage of people, and you are the cheapest manpower for them, they will always send you for work, and per day on an average you get around 70–80 Euro for full shift, and some students work kind of full time by not going to universities and spending more time to earn more and more money at the cost of education and grades.
If one calculates this whole thing with the vision you are just sending your full-time salary one or two-semester away. As early as you finish your study there is a high chance of getting the amount of money you earned by doing the part-time job for one-two semester in just two months. So keep your vision and priority in your mind. Just don’t look at the short benefits of earning 80 Euro in a day.
I have managed successfully my finance with this strategy, I had advantages of living in Big cities like Berlin, Hamburg and now Hannover so things worked out for me very well. As I did my Course in German taught Programme so language was never a barrier for me, as I was able to work without any limitations.
So if you are good at communications (English and German) and not a lazy person you will most probably survive with student job during your study. Other factors have influences but it can be overcome by efforts and little bit discomfort and optimum level of luxury.
Good luck! You can also watch the animated explainer video for this question in this video.