can not download or upload on CS5

Can you connect to your server with a 3rd party S/FTP client like Filezilla.  If not, Dreamweaver is not the problem. 

https://filezilla-project.org/download.php?type=server

If Filezilla does connect, then your DW site definition file might be corrupted.  Create a new one and delete the old one.

These instructions are for Dreamweaver CC as I don't have CS5. 

1. Go to Site > New Site >
2. Enter a name for your site definition and the location of your local site folder.  Example, C:\MySite\
3. Click on Servers tab.
4. Click the + sign to add a new remote server.
5. Enter the S/FTP credentials and Root Directory your host told you to use.
6. Click the TEST button to confirm your connection.

Post back if you have any questions.

NOTE:  If your server has been updated recently, your CS5 software may be too outdated for you to keep using. 

The web has changed a lot in 10 years but CS5 hasn't been updated in ages.

Next time you try to connect to FTP click on Site-->Advanced--> FTP Log and let us know the specific FTP error number being returned to you.  Otherwise you can go to Site-->Manage Sites and click on the servers and look at your server settings there.  I'm assuming something here is incorrect based on the initial message, but you can try looking into "More Options" on that screen and enabling passive ftp if it is not enabled.

Also when do you mean your server host says your settings are correct but you don't know where to check yours?  Did you send your settings to them to verify?  What exactly are they saying is correct?