the easiest step is to revert back to 5.2 or 5.3 unless you are using machighway (they seem to not want to do anything)

step 1..
Back up

step 2..
make sure you have everything backed up

step 3..
depending on the version you are running you might be able to manually upgrade

**or

create a server on your computer running a lower php like 5.2 and with your back up move the site to your local computer and run the upgrade process to the latest version and move the site back to your server

there are docuentation how to set up a wamp server
http://www.concrete5.org/documentation/installation/hosts/installin...

***or you can take your back up to a new server(different company)that allows a lower php version

*others with issue*
http://www.concrete5.org/community/forums/installation/unable-to-up...

I cannot log in.

you have to change these things on the server side in cpannel not in concrete5 ..

you can post your issues in the jobs form and see if someone can help you in your price range if your not comfortable getting into the server