Good day!
I can optimize your 3CX and Mikrotik Router for You confidently and quickly because I am MikroTik certified network engineer (MTCIPv6E/MTCTCE/MTCNA) having over 10 years of experience in configuring, maintaining and troubleshooting of enterprise network devices (routers, switches, and firewalls) and Linux servers.
What type of VPN (L2TP/IPSec, IKEv2, OpenVPN) and Linux distribution (Debian, RedHat, Slackware) do You use?