I'm trying to test the speed of my site with
monitoring-transactionnel.com I have an error
Vary: Accept-Encoding with Google but I do not know how to settle the problem.
Those are Google Ads scripts, you can't take control of those scripts nor the way they are served.
You shouldn't worry about them, generally these scripts are really small and Google brings them at Speedlight, and most of the time on your page onload, but if you're still so much concerned about them, you can only remove Google Ads from your page.
Oh also, as I can read here, load show_ads.js once, these scripts are only loaded once, next time they will load from cache.