Macbook stuck in a loop during install of Mojave from Sierra

Hi there- stupidly i decided to update my macbook from sierra to mojave. It is now stuck in a loop showing error log. - when i try restarting the hard drive it keeps taking me back to the install process, only to show the error log once more. How can i break the cycle?? Have tried recovery mode, safe mode but was so slow i quit start up. Followed other peoples advice on restarting but on mine it keeps trying to install mojave every time i restart. I really dont want to lose my data on the drive. I dont have time machine backup. Is there any way i can bypass the comp trying to install this **** update. Really hacked off with apple and all this. Hope someone might be able to help, thank you