Maintanance page stays forever, after trying to update fro backend


I have tried to update my shop to 5.5.4, all the requirements were met, and when i hit download it downloads, processes and then puts me into the maintanance mode, and I don’t know how to update.

The only thing I could done is that i deleted the update folder from files folder, but then I am again stuck with the old version 5.4.2. Any suggestions how can I execute the update ?