I downloaded the source from git and went through all the steps to set it up but as I finished the build of my project it started to say that it couldn’t find some function. I tried to locate it and by the looks of it some of the files aren’t included in the source even though they are, I guess their path is incorrect or something looked online for answers but didn’t find much. Anyone can help?
Ps: I already rebuild the source a few times nothing changed.
(Assuming you are talking about UE4’s source code on Windows)
Beyond that you may need to do some sleuthing to determine what differences if any exist between the engine source on your machine and Epic’s repository. This may sound daunting as there are literally millions of lines of code to check but if you use a tool like the Github Desktop client it should be able to highlight differences for you quite readily.
I did all the steps you said, didn’t rush anything, git hub desktop is quite not saying that something is different. I updated visual studio made like 5-6 clean builds already just to see if something changed, every build 4 hours but still nothing.
The only other thing i can think of is that you may have different versions of the compiler having a conflict. The error message will usually reflect this though.
Without more information it is hard to know for sure, sorry!
Complier you mean visual studio? if so I tried to build on 2017 and 2019 but the result was the same. Sadly I don’t even know where to look for the information the only errors it shows is that there is an “unknown identifier” and when I click on the includes with Ctrl it can’t find the path on the same cpp where the “unknown identifier” is located .
Just reading what is in the Output window in Visual Studio after a compile fails can be very illuminating, understanding it is the hard part. If you have two versions of Visual Studio going that will likely mean you have two versions of the c++ compiler. Maybe try making sure you only have one installed and doing a fresh build in a new folder and all? Lots of time waiting for paint to dry i know, but i am just giving ideas at this point. I know its probably not very helpful. Sorry!
It’s alright after 10 tries of new builds I think I got it, I was working on the release branch now I cloned a different branch and installed “Unreal Engine Installer” on my visual studio. Don’t know with one fixed it but now by the looks of it working thanks for the help. 
Fixed same way