If I chose to let Xert sync with Garmin Connect, is it only future workouts, that will be synced or is it all my old ones as well? I got a shit load of workouts in GC, I dont wanna have synced, so cant really try 
GC doesn’t allow us to go back historically. You can use Strava, if you happen to have an account or plug in your Garmin to upload the FIT/TCX files manually.
bonjor je narrive pas a charge sur garmin connect une seance d entrainent xert
Did you record it with your Garmin? Is the FIT or TCX file on the Garmin device?
bonjour ce que j ai fait jais enregistre le fichier sur mon ordinateur et après de garmin connect je vais le cherche et la il un message d’erreur
Hello Laurent. Please send an email to support@xertonline.com with specific details and screenshots and we can have a look at it for you.