pgAdmin Remote Access through Putty throws Password error

I tried to access postgresql-server remotely via pgAdmin on Windows through Putty-Tunnel as explained here:

https://www.linode.com/docs/databases/postgresql/how-to-access-postgresql-database-remotely-using-pgadmin-on-windows/

However, each time I try to connect with pgAdmin, I get the following error message:

Unable to connect to server:

FATAL: password authentication failed for user "postgres"

Putty-Tunnel:

• Source port: 5433
• Destination: 127.0.0.1:5432

pgAdmin:

• Host name/address: 127.0.0.1
• Port: 5432
• Maintenance database: postgres
• Username: postgres
• Password: **** (password for postgres-db-user, and not linux-user)

What am I doing wrong or missing here?