In general while updating mac if there is not much space on your Mac drive the installation will stuck in between at around some percentage it will freeze. The installation will take around 2 to 3 hours to complete in some scenarios and in freezing condition it may not end and to verify freezing press command + L on installation page to check if OS is installing.
If you are not able to turn on Mac and receiving black screen error to solve read to Fix Black Screen Error on MacBook Pro. But if operating system sierra stops installing then the best procedure is shown in the blog below to solve Mac OS high sierra installation stuck problem and complete you installation procedure for Mac.
Steps to Fix Mac OS High Sierra Installation Stuck:
METHOD1: FORCE RESTART MAC
Step1: Press and hold power button until your Mac turns off.
Step2: Wait for 5 minutes and restart the Mac and try to install again.
METHOD2: INSTALL IN SAFE MODE
Step1: Restart Mac while holding shift key and release the key after apple logo appeared.
Step2: While in safe mode open apple store and click on system updates to get High sierra.
METHOD3: RESET NVRAM
Step1: Restart Mac and while turning on press and hold command + option + P + R.
Step2: Now Mac will restart and check for updates and if found install Updates.
METHOD4: REINSTALL IN RECOVERY MODE
Step1: Restart Mac and press command + R to enter recovery mode.
Step2: Now press disk utilities options and choose on first aid services.
Call Mac Support Number +1-877-232-0717 to Fix Mac OS Sierra Installation Stuck Issues
If above given methods is executed by you step by step but still having same issue again you need to contact Mac support number or you can also get in touch with Mac OS Sierra Support team. To get in touch with certified technical professionals you are required to call toll free number +1-877-232-0717 to get round the clock support.