OpenWRT with OpenVPN for second gateway

Good evening,
I hope my english is good enough to explain you my plan and problems:

I got an AVM FritzBox for internet access for all my devices (192.168.111.xxx).
I have a TP-Link Archer AX23 with the newest OpenWRT + OpenVPN working.

How is it possible, that only special devices (manually set the gateway to OpenWRT Router) work in my LAN but use the OpenVPN connection?
Or do I have to create another Network like 192.168.112?

I want devices to use the VPN Connection and at the same time have access to my local NAS
:thinking:

Ahh, that's the first time I use OpenWRT so maybe a Newbie answer or HowTo would be perfect :wink: