Power in my car cuts out and comes back


the electrical current works strangely; it rises and falls with the car's revs, and when I use the turn signal and press the brake it dims as if it's about to die
Translated from TurkishCheck the battery terminals — one of them might be loose.
Translated from TurkishI'll try it, thank you.
Translated from TurkishIs the car even charging? Have you ever measured it? Take a measurement with a multimeter if you want.
Translated from TurkishI'll take a look, thanks for the info.
Translated from Turkish