The short answer is that you can't. Your four questions give you four pieces of information: the top four of eleven options.
one single question which asked for the person to rank their choices in order of importance from 1 to 11
would have eleven pieces of information: the ranking for each of eleven options. The issue is that there's no meaningful way to distinguish between the results that were not selected as one of the top four. You have no way of telling which one should be 5th and which is 11th.
However, if all you're interested in is the aggregate results, you could do the following:
For each question and each option, assign a ranking to that option (1 if elected as the most important, etc.).
If the option wasn't selected, give it a ranking of 8 (the average of ranks 5-11).