Please help us help you and fill where relevant:
LimeSurvey version: 7.5.1+261007 
Own server or LimeSurvey Cloud:
Survey theme/template: fruity
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first the layout editor of this theme changed completely in contrat teh monochrone ones. 
most importantly, the bootstrap buttons now in all surveys, all appear in one row and this cannot be modified.

Hi,

first the layout editor of this theme changed completely in contrat teh monochrone ones. 

Do you mean by "layout editor" this new editor? If you do not like it, you may switch to the classic editor.
This is in my opinion still the best option.

And I do not see any changes or any differences neither in the theme editor nor in the theme options.

And what are the "monochrome ones"?
Screenshots??

the bootstrap buttons now in all surveys, all appear in one row

File a bug report.
[url] community.limesurvey.org/bug-tracker/ [/url]

Joffm