Newbie Workout fail - Tunnabora

Failed today and only got half way through
My question is that I had a moveable line on 5he display showing 100%
Are you meant to change the % down if you are struggling so you can complete workout?
Newbie question any help fully appreatiated
TIA

Yes, adjust the workout intensity down in an attempt to complete it.

But you should ask yourself why you weren’t able to complete the workout as prescribed. Was it that you were carrying too much fatigue, nutrition related, or was it just too hard. It’s possible that your FTP may be set to high. Tunnabora isn’t a limit pushing workout IMO, and under most circumstances you should be able to finish it. It would be beneficial to identify why you were not able to finish it.