My university provided my a smartmeter (landis+gyr e750) for my bachelor thesis.
The smart meter is connected in LAN and uses a a special protocol (SML - Smart Metering Language)

I was trying on my own and with a help of a other forum without success.(vzlogger).

I found a 6 year old git repository (github.com/wkleiminger/pylon[/) where someone developed a script or anything to read the data.

What do you think is it possible to configure a raspberry pi 3 to collect this data and provide it a json/database?

If there is anyone who feel confident about this i could pay for helping me out.

Does not look like your question is specific to OpenWrt; you will probably obtain more help in other forums.

Taking a very quick look at pylon/smlogger, I see that it is a C program, not a script.  Also it appears to be made to upload the data to the Google Power Meter server, which does not exist any more.  It looks like it can get data from the E750 meter, but the other side that stores or otherwise handles the data will need to be written.  That would be done on a PC then port the final version to a standalone machine like a router running OpenWrt.

You can port C programs to OpenWrt by writing a Makefile for OpenWrt's build system. I used the "picocom" package as an example of a package that is basically a single C file.