Lazy/Busy Professor does not give me my confirmation I have done a short summer research internship at a department of a famous University in Europe. Unfortunately, this was last summer and I reminded my professor several times now to give me some sort of written confirmation that I actually stayed at his department.(3 times per E-Mail and one time, when I left him). He always said that he will do it, but he always pointed out that he is very busy currently. 

Do you think this sounds true? I mean, it has been half a year now and apparently there is not much to do about it instead of just waiting or is there? I also just asked for a few lines, not a confirmation letter of anything similar and I also told him that I would need this for my home university(Which was true)- but he did not really react upon that.  

I do not want to pressure him by being more "rude" in my mails, this is not the way I deal with such situation, but I think his behaviour is very annoying and I want this piece of paper now. 

How would you deal with that?
I would address this by contacting the professor's administrative assistant or secretary. Usually, such "form letters" do not need to be actively written by the professor in question—just signed by the professor. The assistant can prepare the letter, and get the faculty member's signature; in some cases, the assistant may even have a digital signature available, so the professor's direct involvement isn't even necessary.