Have you been overwriting the web.config with a version from an install package or with the web.config from a file backup that was taken before you commenced the upgrade process? If the first then you have overwritten the machine key which will make the site unusable.

Have/ can you get a back up of the files and the database from before you started trying to upgrade? If so I would try and set these up locally and get it working. Then if you can get it working replace the production site with the working local copy.

Then check all the 3party modules you have one the site to make sure they will work with the newer versions of DNN.

Then retry the upgrade in steps as suggested by Sebastian taking a full back up of files and DB at the end of each step.

HTH

Antony

I finally gave up so I subscribed to PowerDNN hosting company and uploaded all my files with. they were able to restore my site.

I think they finally did what you recomended at first which upgraded to dnn 5.6 and that seemed to solve the problem.

I really appreciate the time you took to respond. Thanks