Those descriptions are located in the Tutorials txt from the assets, line 8036 onwards
"Tutorial","Suppliers","","HUDText","Your fuel supplier will impact how fuel efficient your car will be. The better your fuel efficiency, the further you will be able to push your car in races.","PSG_10010296"
"Tutorial","Suppliers","","HUDText","The engine is the most important (and most expensive) part of your new car. Engines impact fuel efficiency and car improvability.","PSG_10010297"
"Tutorial","Suppliers","","HUDText","Your material supplier impacts the car's tyre wear and tyre heating, with a focus on the wear rate. Better chassis materials will mean your tyres last for longer in races."
"Tutorial","Suppliers","","HUDText","Your brake manufacturer impacts the car's tyre wear and tyre heating, with a focus on the tyres' heating. Having a better brake supplier will mean your tyres' heating will be more consistent."