Maybe this option might be handy.
https://community.openvpn.net/openvpn/wiki/Topology
subnet topology
is the current recommended topology; it is not the default as of OpenVPN 2.3 for reasons of backwards-compatibility with 2.0.9-era configs. It is safe and recommended to use subnet topology when no old/outdated clients exist that are running OpenVPN 2.0.9 under Windows.
in my case it solved so many issues 
, now just pushing just gateway ip in config. Tested on droid,win10,rpi3+ devices.