Sorry its a B+
I have followed various of guides, but a friend of mine told me the problem is on Githubs site.
It's definitely not github. Something's going on with your side.
Don't try to clone a branch, clone the repo. Then, switch to the branch you want.
I have downloaded the files now, but I am not able to use the command qmake to start creating the qt
Did you install all the prerequisite libraries and packages to be able to build? Honestly, I'm not sure that B+ will have access to enough available RAM to actually build the core to begin with, unless you're doing some fancy virtual RAM swapping with an attached external drive. There are a number of tutorials on how to build Bitcoin Core on a Pi; however, if you've never used Linux before, I'd suggest you do a bit of reading on the OS and how to get around in it prior to attempting.