Hello.
I have installed simple forris openvpn module, but as i can see there isn’t any settings, only defaults 
Also I have tested the speed in 100Mbit/s channel. Over vpn i get only ~20Mbit/s.
Are there any issues to get better speed?
for example through beta.speedtest.net
try from phone over LTE+ (~90Mbit/s without VPN) and then notebook + wi-fi from another location (~200Mbit/s without VPN).
With VPN I can’t get more than ~20Mbit/s
Yeah, I have read them, but there is no guide how to speed up.
Do anyone get 80-90Mb/s speed? Or is there any guide how to speed up?
I have similar issue … now I have also only max 20mbps over vpn, but last year it was OK … and maximum speed was comparable to speed without VPN immediately (not same, but around 10% less , which is usual).
I have also noticed that if I try to download big file (lets say 10GB per file) then speed can grow … but it happens for every file, where it starts on 20mbps , keeping this speed for couple minutes and then it grow up to 90% of internet speed what I have.
Any idea or help for non skilled user? 
Noone from experienced users dont know what can cause this issue? 