i like this one its very high quality i wish there were more of these cars

Thank you so much man :)

First i used a tool called "GbxDecompress", which you can download on the very bottom of this wiki page somewhere https://wiki.xaseco.org/wiki/GBX

Then i got a tool called "Noesis" from here:
https://richwhitehouse.com/index.php?content=inc_projects.php

Installed a Noesis GBX plugin "fmt_Trackmania_gbx_PC.zip" from this post here:
https://www.vg-resource.com/thread-37380-post-661544.html#pid661544

Drag the MainBodyHigh.Solid.Gbx onto the decompressor, load that decompressed model in Noesis and whoop de doo, you can export the model as fbx, obj or whatever from noesis and use in in blender.

How did you convert the original .gbx file??

I'd eventually look at how lvs or symfphys works. But I couldn't find any proper documentation on how to make mods for it

Would've been cool to have that on LVS or simfphys, but still, amazing work.