-If i use a weakness to magic 100% spell on an enemie twice will it stack to 200% and so on?
If you cast the same spell twice in a row your target will end up with 200% Weakness to Magic.
-If i use a weakness to magic 100% (A) spell and make another weakness to magic 100%( B ) though i name the spell differently and cast spell A & B on enemy will it stack to 200%?
Your target would have 100% Weakness to Magic from the first spell and 200% Weakness to Magic from the second spell. Together that would give it a 300% Weakness to Magic.
-If i use a weakeness to magic 100% (A) spell and make another weakness to magic 100%( B ) and cast spell A, spell B, spell A again and then spell B again too, will it stack to 400%?
The total Weakness to Magic in this case would be 600%.
When you cast spell A for the second time your target already has a total 300% Weakness to Magic so the effect of spell A is 400% Weakness to Magic. However, the effect of the second casting of the spell replaces the effect of the first casting so you lose the initial 100% Weakness to Magic. You are then left with 200% Weakness to Magic from spell B and 400% Weakness to Magic from spell A.
I made an ebony bow with these enchantments and in this order:
Weakness to shock 100% for 6 secs
Shock damage 16 pts for 1 sec
Soul trap for 1 sec
-If i fire an arrow at my enemy will the weakness to shock take effect on the first shot as i have the shock after the weakness therefore doing 32 shock damage points?
No, the weakness will not take effect on the first shot.
-If i fire two arrows at my enemy will he only be weakened by 100% and not 200% therefore doing 32 shock point damage?
You would do 32 damage.
Note also that Weakness to Fire, Frost, or Shock stacks differently than Weakness to Magic. Weakness to Shock only increases Shock Damage, it doesn't have any effect on Weakness to Shock. On the other hand Weakness to Magic has an effect on all magic spells and that's why it makes itself stronger if you cast it repeatedly.
-When i fire the second arrow into my enemy he will be weakened 200% by shock but will the timer of my first shot ( timer as in the 6 secs of weakness to shock) reset to 6 seconds again?
When you fire the second arrow your target still has only 100% Weakness to Shock. The only thing that happens in regard to the Weakness to Shock effect is that the timer is reset back to 6 seconds.
-Does it matter where soul trap is on weapon, as in first enchantment on the weapon or third as i have it?
Not sure, but IIRC the last effect of a spell is actually the one that is applied first.
-So if i keep firing arrows into a strong enemy, will his weakness to shock keep increasing and reseting the timer of the first shot?
The Weakness to Shock will be a steady 100%, only the timer will keep reseting.
I had more but i dont wont to bore you guys, a simple yes/no answer will do, but if u can elaborate on any of them i will appreciate that too, cheers guys sorry for being such a [censored] but unless i get things explained to me like a 5 year old i wont undertand

its just the first time ive looked into stacking, poisons and enchantments really so all of a sudden ive gone from doing nothing to everything and am getting a little overwhelmed ( i have read uesp and sometimes they confused me even more )
Here are the basic rules for how these things works:
1. If you cast the same spell or use the same enchantment on a target twice in a row, the second use repalces the first use. The second time you use the spell or enchantment will only reset timers for the effects of the first one.
2. Weakness to Magic will increase the effect of all hostile spells and enchantments. If you cast a spell with Weakness to Magic twice on the same target the second casting of the spell will be amplified by the Weakness to Magic from the first casting. That is why Weakness to Magic is the only effect that actually stacks with itself.
I hope that was clear enough, but if you want I can provide more examples.