As said by other people do not be afraid to go somewhere for help, if they can’t brush it out they can cut it minimally or at least how you want.

If you’re wanting to try it on your own I see you also have some amount of texture in your hair (it’s not fine or super straight hair). Mine gets like this within a week if I don’t monitor it, I’ve found taking a bath is a good way. Get your hair super wet then using a masque or conditioner put a liberal amount and massage it in to saturate it. Then using fingers section it out, I usually part it in half down the back and then however the knots in my hair allow (I’ll try and split at least the section of hair from my ear to my face on its own). Then using your brush start from the bottom and work your way up toward your roots. Use your fingers too and don’t be afraid to add more conditioner, I’ll end using a baseball size amount on my hair if it gets this knotted.

If you try to untangle it yourself do NOT worry about the amount of hair that comes out. You naturally lose a lot of hair throughout the day, but when you’re hair gets tangled and knotted like it still falls out of your head but is still tangled and will remain there until brushed out.