Hi Renan.
Excellent explanation from Sylvia. She’s encouraging you to keep trying because training your ear is one of the best things you can do in learning guitar.
I’ll just add a few points…
You don’t need to know any music theory at all to start training your ear. You don’t need to know the name of the notes you play or names of the intervals - you can learn all that later. You just need to hear the different sounds of the different notes.
You need a song. The song should be one that you know the melody of really well and you recognise it instantly when you hear it because it’s ingrained in your mind. I’ll not make any suggestions because you might not know them.
Yes it can be frustrating at first but you’re not trying to find the whole song. The first two notes will do for now.
So think of your song. The first two notes. Hear them in your mind. Sing them if you like.
That first note: play a few notes anywhere on the guitar until you find one that matches your first note.
Now the second note: is it the same? Is it higher? Is it lower?
Play your first note again and then the notes nearby till you find the second note.
Once you’ve found those first two notes, that’s it!! You’re on your way. You’re playing by ear!!
Don’t be frustrated by it, have fun with it! 
, I’ll keep practicing, I’m going to master going down first, and then going up, it’s better for me to learn bite size, just like learning on keyboard.
but I kinda want to have one again so who knows 
