The fastest way is to use the Adafruit RTClib. It is in the Library Manager in the Arduino IDE.
There is also a TimeLib, which is more basic, but also more extendable.
The Arduino Uno is a 5V board with a 5V I2C bus (The SDA and SCL are between 0...5V).
If you power the DS3231 module with 3.3V, then it has a 3.3V I2C bus.
That means your I2C bus is not good, it barely works.
You can power the DS3231 module with 5V, but not if you have a rechargeable battery in it. That module has a bad charging circuit. You can disable the charging by removing the diode and put a normal battery in it.
Your DS3231 module costs less than 4 euros: https://www.aliexpress.com/item/1005003101038004.html
You paid 8 euros for the exact same module.
All this trouble with the module, with 5V and 3.3V, with the I2C, and so on, that is what you get when you buy the cheapest things. Adafruit makes good quality modules, they test everything they sell, they don't use fake components, they have a forum, and so on. They don't cheat, they tell if a module can be used with 3.3V and 5V.
DS3231: https://www.adafruit.com/product/3013
Look there for a good tutorial, they also explain how to install the RTClib and how to use an example.
Are you feeling where this is going ? Your DS3231 might be a counterfeit, there are many bad tutorial on Youtube and Instructables, if you buy the cheapest crap then it might not work very well or maybe only for a week or maybe only in a certain situation.
Be careful, if you buy a more expensive module from a local seller, then it might be the same as the cheapest crap on Ebay/Aliexpress/Amazon.