Format time impossible

Good Morgning

I would like to send several pieces of information by e-mail, including the date and time of this type.

On: XX-XX-2024
à : 11:40:00

for the date I was able to format as I wish but for the time I can't add the two extra hours I have compared to UTC time.

I have a data update that adds two hours to my time
flow.correct_UTC
tostring(AddHours(Flow.StartDateTimeUtc, 2))

but then I get an error message when I want to set my new time:

i think i have the wrong approach but i don't know what to do if anyone has the solution please