Hallo everyone,
A couple of days ago I bought a l2c 20x4 display module (https://elektronicavoorjou.nl/product/i2c-20x4-arduino-lcd-display-module/)
I was wondering what kind of fun projects I can do with it and to see of you guy's have some interesting ideas.
Thanks in advance! 
Add a Real Time Clock module and make an alarm clock.
Add a BME280 temperature, humidity and pressure sensor and make a weather station.
I saw this yesterday, which uses a similar screen to yours:
https://forum.arduino.cc/index.php?topic=664285.0
Try searching with your favorite search engine for "Arduino Projects" There are a lot of books, paper back, papers etc available on line for all levels of experience. You will also find project kits etc. When you start use simple projects and understand the software and how it works. This is not an over night learning experience. This response is to help you get started in solving your problem, not solve it for you.
Good Luck & Have Fun!
Gil