This ***** took my souls and one humanity from me xd

Then be careful and don't be such an egotistical dumbass.

The following strategie worked well for farming for me:
If you come from the Demon Ruins' side of the bridge (only after you open the shortcut), you can run up to it (it won't notice) and hit a heavy meele strike (both handed) on his tail. If you turn around and run back (beware of his lightning projectiles) you can hide sideways (when you just ran off the bridge). He will turn back after a few moments (to the Lost Izalith side of the bridge). Wait a few additional seconds after he is in his default move pattern (5s is not enough, 6s will do), and you can repeat this pattern until he is dead.
Note that it will take quite some time though (my lightning axe +4 in NG did 241 damage) as you will probably not get a second hit on him. On the other hand you will be able to take him down without getting hit at all.

For the titanite Demon guarding the Darkroot garden entrance, try moving to the left as you come down the stairs. It will keep using ranged attacks, but they can be blocked by a broken pillar right in front of it, but leaves enough of it exposed you can casually shoot arrows without fear of taking any damage at all.

titanite demons are NOT weak to lightning, they are resistant. Using lightning is essentially challenge mode.

A general strategy for titanite Demons is to run to their left side (the side without the weapon) and stand next to it between its arm and tail. Hit it once or twice depending on your speed and if it stops moving it will probably use its jump attack so just run past its tail and it should miss then run back and repeat.

i just stand from a distance and blast my arrows at their ***** faces

just use some gold pine resin

Can you cut its tail off?