error when deleting view when I try to delete a view from the views module, I receive the following error:
error_1

Trying to save a new view shows this:
error_2

Any idea how to fix this? 

I also cannot delete the view manually as my phpadmin tells me that there is an error and that I have to configure session.save_path... but I cannot find any file named session.save_path on my server.

Please let me know if you ever had this errors and if you know how to fix this. I invested 50 hrs to develop new functionality and I cannot risk the website goes down for days... 

Thanks in advance!!
It sounds like you've got some pretty serious problems here.

The fact that you can't use PHPMyAdmin because of the session.save_path setting (which is in php.ini by the way, it's not file name) would suggest that something on your server has changed. At a guess I'd say your web server no longer has write access to the session folder, but without seeing the full error message it's hard to say.

The fact that the you can't enable the db log module is also quite worrying. That module defines the watchdog table upon install so the fact that it's missing might suggest Drupal is having problems creating database tables.

The best advice I can give is to get a local version of the site up and running, with permissions for files/databases set up in a way you know is correct, and see if you still have problems.

If you do, then you know that the problem is somewhere else and you should start methodically disabling and uninstalling modules until you can narrow down the culprit.

If you don't, then you know the problem is with the live server configuration.