Welcome to the community, @TunLin! You could do it as outlined in the image shared below:
In the survey tab of the XLSForm
In the choices tab of the XLSForm
Data entry screen as seen in Enketo (when nothing is entered in Q1)
Data entry screen as seen in Enketo (when something is entered in Q1)
Reference XLSForm
Skipping.xlsx (53.3 KB)
Note: You could learn more about skipping through our support article Adding Skip Logic.