2 Lan get together

Hey, sorry to disturb anyobe, but perhaps you will give me an advise:

Following Problem:
i do have a Productive network and a network only for developement

Now i need to get both together
there is an ipfire on both ends…so one of it has
blue (ipaddresse from the produktive network)

the connection shall be without using the red

at the moment, there is a vpn connection between both networks…it works, but it is slow

so i want to give the blue an ip adress out of the productive lan, make an routing entrie inside the switches

I created firewallrules like blue is allowed for TCP and UDP

After that I was able to get a ping from the developement network to the productive network and vice versa…which means, i am able to ping the green interface of the ipfire to the developement network

But i am not able to get through…May I ask after some advice, please