Constructing, repairing, or going on missions takes time.
If you don't like to wait to keep playing, you can use Time Skips to accelerate the time.
To do that, simply tap the watch at the top of the screen and drag it to the right as much as you like.
You can skip as much time as you want with one time skip.
For example, you want to complete a building so you can send that survivor on a mission. If you don't want to wait, just drag the time to the marker that tells you when the mission will be finished. The game will ask you if you want to use a Time Skip.
After confirming, the time will jump forward to the designated time and you can keep playing.
Of course, you can skip the whole day with just one Time Skip, too.
Just make sure to not waste Time Skips with unnecessary or accidental skipping.
Even if you only skip 10 minutes, it will cost you a whole Time Skip.