I have a single entry (Schengen)visa to germany as a tourist and I stayed here now for one month, then I applied a job in Hungary, the company in Hungary requested me to go to Hungary for a job interview, I am worried that if I go to Hungary for interview the German immigration will stamp my passport for exit (if I am correct) in that case, if I did not get the job in Hungary how can I come back to Germany? is the German embassy in Hungary allow me to apply for a visa, if possible to get the visa, how long it takes? and one of my concern is ifever that I lose my interview in Hungary I can stay again to Germany and wait for the expiration of my schengen visa. Anybody can give me an assistance what to do please.

I think you will be put under scanner because the visa officials in Hungary's German embassy will definitely figure out your intentions and therefore very high chance of your visa being refused. Moreover according to the Schengen agreement a short stay visa does not allow you to stay more than 90 days per period of 6 months in the Schengen region. Once you leave Germany your visa permit ends and that means you will have to wait 6 months before applying for a new visitor's visa to Germany.

Probably I am not justified when I said about 90 days because I saw that you just stayed 1 month in Germany so there is every possibility of getting the remaining period when you go for a new visa in Hungary and therefore you will have to justify your visit in Hungary as a tourist and I saw that it takes normally 2 to 10 days for application procedures depending on the peak time. For more info you can visit your local alien office in Germany and tell them your intentions of visiting Hungary as a tourist and then see what happens or call hotline number +49 30 5000 2000

A single entry visa allows you to make only one entry. If you leave the country, your visa becomes invalid.

Usually a Schengen visa is a multiple entry visa. Try changing your visa to multiple entry visa. Then you could make more than one exit/entry.