Error establishing a database connection

i tried everything from checking my sql (hostname,username and password) to reuploading the files. please help!!!

That error message is a generic message from WordPress saying that there is “some issue” with the database connection. To figure out what’s actually going on, you need to enable debug mode in WordPress so you can figure out the real error message: Debugging in WordPress « WordPress Codex

After that, you can compare it to the known database errors:

Hi Admin
last 5 days my website showing Error establishing a database connection

i don’t know how to fix it
please help me

I’m glad you posted the message in a topic about the same issue. But next time, please read the messages posted in such topics before, as they usually contain more information about the issue.