Chapter one spell/mathchecked

I know that chapter one was marked as spellchecked, but there still are a lot of mistakes - Hope this helps. Also, I corrected all the mathematical mistakes i could find, manly line 609(old)/619(new). 

Also, i took the liberty to add the title "Formaler Beweis von Satz 1.5" because it was unclear to me, that the following steps were another proof of satz 1.5 (line 147 (new)).

- Spellchecked
- Math corrected

Hope this helps

Aurel