I sent a postcard from Munich (Germany) near Ostbahnof station to my friend in Gurgaon (Delhi, India) on 12th of October. I asked the man how much he said 80 cents. Whether he included the stamp or not or what he did, I have no idea. I am new to Germany. And he said it would reach within a week or two. It is almost a month now, my friend has not received it yet. Postcards are not given any tracking number apparently hence no one has any clue about it. Can someone help me here?
There is nothing that you can do at this point. As you already wrote, there is no tracking option.
Note that the delivery time (1-2 weeks) only means that it should only take so long for your postcard to reach the destination country. Once it is there, it is up to the local post to do the handling. In countries where there is a difference between surface mail and airmail, letters and postcards from abroad will often be treated as surface mail if they do not have a "Priority" sticker on them.
The brochure by the German post actually explicitly states that you should put such a sticker onto your letter or postcard before sending it abroad to request swift delivery (link, page 8 - in German only). You can get these at the German post station for free and they typically do not put it there automatically if you do not explicitly request it. Also, the fee is the same regardless of whether you request priority post or not.
In any case, the 1-2 week are no guarantee but rather a typical delivery time value. The actual value depends on many factors that you cannot influence, including the volume of mail currently in transit.