I've been wondering what the fastest missions are for restoring the thieves guild? It just seems that they just take too long. Are there certain missions that only take about 5 minutes?
To answer your question properly and completely:
This quest requires you to complete "Small jobs" given to you by Delvin and Vex, to restore the wealth and power of the Thieves guild.
To complete this quest properly, you will need to complete 5 of each of the 6 types of job, in each of the 4 main holds.
To explain further: 'The fishing job', assigned by Delvin, must be completed 5 times in Whiterun, then you will be given a Special side quest by Delvin, marking the jobs 'completion'. Rounding the total amount of times you need to complete a 'Fishing job" 24 times.
So in total, there are 144 missions you will need to complete, to finish this quest.