How do I add my own music in a map created with hammer? I tried to follow this video https://www.youtube.com/watch?v=OInSauhy33M
but I could not make it work, you could re-explain it to me in a more simple if possiile?
While how do I add the dialogues of Cave and GLaDOS?

Make sure your music doesn't have any spaces in the name, then put it in your sounds folder. Then in Hammer, you use an ambient_generic in "Raw" sounds and make sure that you have "is looped" unselected if it's not looped and "play everywhere" selected. When in game, if it doesn't work, type "snd_rebuildaudiocache" in the console.

problem solved, I converted the audio into a. mp3 and I changed the frequency to 44100. Now the music you hear

Check that your music is 16 bit WAV. To change it, open the file in audacity and save it as a WAV file. To loop the music, I like to use wavosaur.