I have follow many article but i don't get proper answer please help me, provide me step by step.
2 Answers
Please check with below url for increment or decrement working.
Add Ajax Quantity Increment and Decrement Button on mini cart in Magento 2
You can use for ajax increment and decrement button in minicart Magento 2.3.1. Download below module and use it.
Add ajax increment and decrement button in minicart magento2