Database options are overhead and resist

Hello
I have” Error establishing a database connection. ” error and I took a look at phpadmin and saw database options of the wordpress and my sub-domains (network site) are overhead and when I want to optimize or repair the table I get a “missing value in the form” message and after some minutes I see the options are overhead again.

I removed all the plugins, installed the wordpress too.

What should I do to fix this nightmare?

Thanks