Hi @Aurelija_RutaViluckyte,
The post submission thank you screen message that you see in the web app can not be changed from Connect. This can only be changed from the web designer. However it can now be changed for both web designer and Connect created surveys, previously this was only supported in web designer surveys.
After publishing from Connect, open the survey in the Survey123 website, select the Design tab, and then the Options tab. Modify the thank you screen content and publish the survey again.
Note that the thank you screen in web app does not support question variable replacement (passing values from the form data submission to be displayed on the thank you screen.
Regards,
Phil.