Only few comands work properly in UE4

Hello, my name is , from Chile, and I am new in UE, I am trying to learn how to use the program, but I cant use the comands when I am already inside of a project. Only some of them are working properly when I click on them, but others are not reacting. I tried to find some solutions, like click and then press spacebar, but its not an universal solution. I tried to find solutions in internet, but I couldnt find the answer, assuming also that this can be a normal bug, with an easy solution (or maybe not).
Anyway, I will be really happy if I somebody can help me with this problem, cause I am really exited to start with this program
Thanks for your help!

Can you give a specific example? What command?