thanks for your response:)
If I change the setting from fixed width to responsive in the mobile layout,
then the whole design is broken. Is there any other way to solve the problem?
Many appologies to find you in this trouble.
Would you mind sharing your .muse file with us so that we can investigate and try fixing it.
For sharing the file you can follow the steps explained here - https://forums.adobe.com/docs/DOC-8652.