Hello,
First forgive me for my English level. 
I have an RPI3 with Dietpi installed.
The functions I use are:
Transmission Web
RPI-Monitor
FTP
SSH
All these services work correctly.
I would like to have a secure connection in all the connections I make in my network and from outside it. ( SSL & SFTP )
I think the SSH is already encrypted implemented by the same protocol.
I have read tutorials, but I can not understand how I can implement it.
Can you indicate a place, a guide or a way to start?
If you need any information, I’ll give it to you.
Thank you very much for your help.
A greeting. 