grand prix 3 track

good evening everyone
joined recently, sorry for poor English
I just installed grand prix 3, I downloaded various carset and circuits

I wanted to ask how to install circuits: I copy the files in the folders provided, then copy the dat file in the folder circuit, but when I try to start the race crashes

Thank you in advance

1. install & use gpxpatch (link)
2. copy the track-file (.dat) to a place you like inside your gp3-folder
3. most times you also need to copy a folder with jam-files into "..Gamefolder/Gp3jamsH. Otherwise you see missing textures
4. start gpxpatch -> select the tab for tracks -> load the tracks into slots

5. set debug mode 'on'
6. set track length to 10 km

and let us know which tracks you are trying out, that will help us