@Super Falcon, first thing first. Avoid those agents at ALL COSTS. You might be scammed of your money, end up in some fucked up situation. I have seen terrible things here in Germany.
For industrial work, you definitely need German language (at least B1 or C1). Only exception is that the job is in some big city, like Munich/Berlin, where all of jobs do not require German.
On a student visa, you are allowed to work 365 days part-time, or 240 days full-time. You CANNOT work legally once you use your allowed hours. The only work around this is a work-permit or job visa where there is no restriction on working hours. But, if you work at two jobs, your tax class at highest, class 6. Only way to avoid tax class 6 is have a mini-job (which as limited working hours) apart from your other full/part-time job.
Amazon offers jobs in warehouse without requiring german.
See:
Recruiting Support Customer Secure Login Page. Login to your Recruiting Support Customer Account.
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Minimum salary in germany is 12.5 euros per hour. This is for labor work (warehouse, restaurant, janitors, food delievery, etc). For full-time, you can have 1200-1300 euros after tax.
However, for technical jobs (like engineering), the pay is very high. I got 900-1000 euros for part-time in engineering job, For full-time engineering job, you need german university degree or very good experience (from Pakistan/UAE). The pay for an engineer is 60K-50K euros annum.
Savings depend upon your rent, and living expenses. Living expenses are 300-500 euros. You can bring them down only till certain extent as you have to pay public transport, health insurance (100-200 euros when you are not working), food, etc. Rent is a bitch. You have to share with 4-5 people to have a rent like 200-300 euros (which creates problems of its own). There is no other way around it.
To summarize, do not got for f**king Poland/Malta/etc. Those are very poor countries, and they will make you work like slaves (literally). Avoid agents at all. The way you mentioned work permits, it sounded like illegal work (underground). Police can put you in jail for that, and after that you are blacklisted from EU.
Only come to Germany through legal ways. Not sure, if you would get factory job sitting in UAE. Learn very good german language. Note that german factory may require certificate/diploma of vocational training (Ausbildung).