I need help with my Synology NAS

I need help solving some Synology NAS issues.

Here are few of them:
- access my Synology NAS with my own domain name
- installing multiple websites that can be accessed from internet
- installing Lets Encrypt SSL for the installed websites
- installing Visual Studio Code Server on my Synology NAS

These are just few examples. Others may follow.

I alredy tried to solve them following step-by-step instructions from mariushosting.com and other online tutorials but I wasn't successful.

I have a DS218+ running latest DSM 6.2.x version (I'm not ready to upgrade it to DSM 7.1)

All work will be done via Anydesk or Chrome Remote Desktop.