How to respond to exploding PhD job offer in Europe A few days back I had a second interview with a European university on a project that I really liked. I have also another offer from a Canadian university and am still waiting for 5 other universities for a decision. 

2 Hours after the interview I got the PhD job offer. The very next day I received another email from the department head asking me for a response for the offer I received less than 24 hours earlier.

While I really like the project and the people, I can not make a decision this quickly. I asked him to give me until the the beginning of next week and he agreed. Even by then, I cannot make an educated decisions because there are FIVE decisions that I didn't receive yet.

What would be a good thing to tell the professor by the the time I have to give my answer? I there anything that I can do to have more time before making this decisions ?
Unfortunately, this is a fact of life in academic applications.  Offers come with deadlines, and often you will have to make a decision on one offer before hearing back about the others.  

There are two things you can do:


Contact the departments where you still have applications outstanding.  Let them know that you have another offer, and ask them when they expect to have made a decision regarding your application, or if they are able to tell you anything about your current status (for instance, there may already be a short list of preferred candidates, and they might tell you whether you are on it or not).
Contact the department that has made you an offer, and ask if they can wait for your decision until date X, where X is late enough that you expect to have heard  back from all or most of the other departments, based on what they told you in step 1.  But be prepared to get the answer "no, we need your decision by date Y &lt;&lt; X".  Keep in mind that if you turn down the offer, the department likely needs to move on to another candidate, and they would like to be able to do that before the next candidate accepts an offer somewhere else.


But it is quite possible that you will not have the opportunity to make an "educated decision", as you put it.  You will have to judge for yourself whether you want to accept the current offer, or take a chance on a future offer that may not materialize.