Joomla Forms builder allows you implement Conditional logic fields. Conditional Logic allows you to show fields or sections based on previous user selection.
1. Go to: Components >> Forms >> Your Form;
2. Through a Drag and Drop feature add form elements into editor.
3. Click on the field to open "Field Options" in the right sidebar.
4. Enable Conditional Logic. In the "Field options" select the value to which you want to add "Conditional logic" and click on the button "Add Conditional Logic"
5. Click on the icon "Show / Hide Conditional Logic"
6. Drop form fields into "Hidden Area"
7. Save your Form and enjoy!