Prohibitory symbol on Mac

While trying to fix an issue with my iPhone, I had to install the newest Mojave on my laptop in order to backup my iphone. During the install everything looked fine, my laptop restarted but it froze and then the prohibited sign displayed.

ive been through all the steps to try and reinstall etc .. when it comes to the point where you have to enter a password, I can’t type into the box. There is no typing cursor and when I use the keyboard nothing displays. When on disk utility ‘first aid’ is greyed out, and when I click mount I have to enter a password and again I can’t click in the password box to type it in.

Please help, my laptop was working perfectly before this.

I do have it booked in to be looked at Monday but if I can sort it now that would be best !

Thanks