Hi Mateusz,
On your phone, as it is with most Samsung phones, there are two ways to replace the screen. The usual and recommended way is to replace the screen plus the frame as a single assembly vs. replacing the display alone. Markus' video link shows replacing the screen+frame assembly, as does the link I'll provide.
The two methods both have advantages and disadvantages and require different procedures. For the screen+frame method you basically have to gut the phone completely and transfer all of the interior components to the new frame assembly. The phones are actually made in such a way as to facilitate this, so it's not nearly as bad as it would be on something like an iPhone housing swap. For the screen only method, you have to carefully separate the LCD from the display, clean off all the old adhesive, then glue the new screen onto the frame, clamping it securely until the glue dries. Note that the screen+frame assembly is generally only a couple of dollars more expensive than the screen alone, but that difference can easily be eaten up with the need to buy glue as well.
Here's the screen+frame replacement guide for your phone.
[link|https://www.nadiemellamagallina.com/en/manuales/smartphones-1/samsung-4/samsung-galaxy-m11-1274/pantalla-completa-11345|Manuales / Samsung Galaxy M11 / Fullscreen - Nadie Me Llama Gallina|new_window=true]
The guide is in Spanish but used in conjunction with the Chrome browser's language translation, it is very usable no matter what your native language is.
Replacing the battery is actually part of this procedure, so if you're doing that repair you don't need a separate battery replacement guide. However, if you decide you only need to replace the battery, here's the guide for just doing that.
[link|https://www.nadiemellamagallina.com/en/manuales/smartphones-1/samsung-4/samsung-galaxy-m11-1274/bater-a-11346|Manuales / Samsung Galaxy M11 / Battery - Nadie Me Llama Gallina|new_window=true]