How do I make questions smaller? please see the attached screenshot Thank you very much!

Please refer to the manual - www.limesurvey.org/manual/Question_type_...8text_input_width.29

And www.limesurvey.org/manual/Question_type_...8text_input_width.29 ;)

Thanks ! but I want to make whole container smaller, not just input box , do you know how ?Thank you very much

Extend the theme, and in custom.css add something like :

.question-container { width: 200px ; }

if I want to divide the page into two part,and there are two questions on the horizontal line .what shoud I do? Thank you in advance

I need to gather the questions,there are too much extra space. I add something to custom.css and the page become kind of mass.Need some help T_T Thank you very much!

It's based on bootstrap 3 :
getbootstrap.com/docs/3.3/

Yes, as Louis points out, it is a bootstrap grid. Unless you are well versed in CSS, you should follow the bootstrap rules or the layout may blow up spectacularly on small screens.