How can I change the display

Sorry to say, iFixit being primarily an American company, is light on European phones like the Xiaomi line and as such doesn't have a guide for your phone. There is, however, a Spanish site called Nadie Me Llama Gallina that has exactly what you need.

Manuales / Xiaomi Redmi 7 / screen - Nadie Me Llama Gallina

The site is, as you might guess, written in Spanish, but if you use it together with the Chrome browser's translation feature, then it becomes quite usable no matter what your native language is. I've found the guides to be well done and complete, so I'm confident you will be able to fix your phone with this one.

As you work, take lots of pictures and once. you're done you can use them to create your own iFixit guide to that repair for those who come after you with the same problem. It's easy, fun and will earn the appreciation of the repair community.