Hello Please use simple code 
<field name="your_field" string="string1" invisible="condition1"/>

<field name="your_field" string="string2" invisible="condition2"/>

<field name="your_field" string="string3" invisible="condition3"/>

<field name="your_field" string="string4" invisible="condition4"/>

<field name="your_field" string="string5" invisible="condition5"/>

<field name="your_field" string="string6" invisible="condition6"/>

<field name="your_field" string="string7" invisible="condition7"/>

Hi,

To dynamically change a field’s label in a form view based on a condition, follow these steps:

Step 1: Hide the Default Label

Use nolabel="1" on the field to suppress its default label.

<field name="your_field" nolabel="1"/>

Step 2: Add Conditional Labels

Insert two <label> elements before the field and control their visibility with attrs.

<label string="Label A" attrs="{'invisible': [('some_field', '=', False)]}"/>

<label string="Label B" attrs="{'invisible': [('some_field', '=', True)]}"/>   

This method is XML-only and works well for conditionally changing field labels

 Hope it helps