Can I access my MS SQL (MSSQL) externally?

Yes, this is possible.
The following settings will then apply:

SQL 2005
Host
84.246.4.143

Port
9125



SQL 2008: SQL3
Host
185.41.125.20

Port
9203



SQL 2008: SQL6
Host
185.41.125.20

Port
9203



SQL 2014 Host 185.41.126.25
Port 9144
Host 185.41.126.25
Port 9145
SQL 2016 Host 185.41.126.25
Port 9146
SQL 2017
Host
185.41.125.20
Port 9203

Please note! The host in the SQL Management Studio will then be for example: 84.246.4.143,9135