My mobile is not charging

@redmi938979 not charging and not holding a charge are two different things. It will be helpful if you give us more details. We will need to know exactly what it does when you try to charge it. In the meantime start off by testing the easy things.

First check your charger. Make sure it has proper output. Then check your charging cable. Check to make sure connectors are not bend etc. After that, check the charging port. Clean it of any debris etc, use a few puffs of air to clean it out. If none of this works, get a USB ammeter and see if your phone draws any amperage from the charger. If it does not it is possible that this is a charging port issue or a bad battery.

To check the charging port, use a voltmeter and measure the voltage on your battery connector. Next plug your phone charger in. Now measure the voltage on your battery connector. That voltage will have to have increased. IF not then the issue is either the port or the charging circuit.