I ran into both of these issues as well.
I found the SQL Server Configuration Manager in my Systems32 files.
As for the error when connecting to the server, it took me a while to see that somehow I have two instances of SQLEXPRESS server and it was the other. I am not sure when or how that happened. I am still new and learning SQL. I discovered the second instance while trying to check for updates to SQL in the SQL Installation Center in which a YouTube video said would also solve this issue.