Motherboard is not working

Aamina, on your phone there are two different ways to replace the screen; the recommended way is to replace the screen plus the frame as a single assembly; that way the screen comes already attached to the frame so you don't have to worry about gluing it in place or not getting it sealed against liquid ingress. The disadvantage is that you have to basically gut the phone - remove all of the components inside it - and move them to the new housing. It's actually not as bad as it sounds, as most Android phone manufacturers make it reasonable straight-forward to do so.

The other way to do this replacement is to replace just the screen itself. That means taking apart enough of the phone to get access to the display connector, then separating the old display from the frame, cleaning off the old adhesive. Then you have to glue the new screen onto the frame and clamp or band the screen to the frame until it dries. It's not quite as safe in terms of securing the screen, and any savings over buying just the screen vs. the screen+frame is usually offset by having to buy glue; in other words the price difference is usually minimal.

The two procedures require completely different sets of instructions, so if you decide to do the screen by itself you'll need to use this YouTube video.

Realme 5i lcd replacement/realme 5i display replacement/realme 5i screen repair - YouTube

Otherwise I've located a written guide for the screen+frame assembly replacement from a Spanish site called Nobody Calls Me Chicken. It is, of course, written in Spanish, but used with the Chrome browser's translation it is quite usable even if you don't speak Spanish.

Manuales / Realme 5i / Fullscreen - Nadie Me Llama Gallina

The screen itself is easy to find; I saw examples being sold on sites like Amazon, eBay and AliExpress, among others. Here's one selling the screen both with and without the frame, so you can pick which one you want.

For OPPO Realme 5i LCD Display With Frame For RMX2030 Display Touch Screen Digitizer Sensor Assembly Realme 5i LCD Replacement - AliExpress

That should be everything you need to know to get your phone working again. Good luck, and feel free to ask questions if need be, and be sure to let us know how it all turns out for you!