Ich bin kein Mensch, der sofort mit jemanden aufhören kann zu lieben.
or
Ich bin kein Mensch, der sofort mit jemanden zu lieben aufhören kann.
and my requested meaning in English is "I am not a human than can stop loving someone instantly".
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Sign up to join this communityI think this would be better
Ich bin kein Mensch, der einfach aufhören kann, jemanden zu lieben.
Ich bin kein Mensch, der sofort mit jemanden zu lieben aufhören kann.
Problems arise post-comma, however.
mit jemanden
mit is a dative preposition so one must say
mit jemandem
In reality, we don't really need that mit there because lieben is transitive, which means it must take a direct object. Since it's the direct object of lieben, jemand- becomes jemanden in the accusative.
So now our sentence is
Ich bin kein Mensch, der sofort jemanden zu lieben aufhören kann.
Der is a relative pronoun which introduces our appositive, the phrase that describes the antecedent (Mensch) further. But we have things in our appositive that do not describe Mensch but rather tell what ich, the subject does. Those things namely are...
jemanden zu lieben
I love someone but that however does not shed any light onto what that Mensch is doing. So it has no place in our appositive (it goes outside the commas behind the appositive). Hence our sentence is now...
Ich bin kein Mensch, der sofort aufhören kann, jemanden zu lieben.
Our work is almost finished! It was previously mentioned earlier that einfach works better in this sentence than sofort stylistically and connotation-wise. So our final product is...
Ich bin kein Mensch, der einfach aufhören kann, jemanden zu lieben.
The mit is inappropriate – strictly, you are suggesting that you’re not a person who can stop loving with somebody.
Ich bin kein Mensch, der sofort aufhören kann, jemanden zu lieben.
This is one step better, but it’s still awkward. »Ich bin kein Mensch« is a slightly clumsy formulation – correct, but you’d never hear a native speaker use it.
Ich kann nicht einfach aufhören, jemanden zu lieben.
Finally, something better. The best, though, would be to say
Ich kann nicht einfach aufhören zu lieben.
Every language has a logic, and German has a lot of it. A language, to get all Sapir–Whorf, conditions how you think by conditioning how you can express the same idea. Thus, while the second translation is ok, I think the last one gets it across much better (unless you want to put very specific weight on someone, in which case, however, you might feel you want to define that term).
I would choose the first sentence which is
Ich bin kein Mensch, der sofort mit jemandem aufhören kann zu lieben.
because the verb aufhören is one of the "zu construction verbs" that means the preposition zu is needed. And instead of jemanden, it's jemandem because mit takes the dative case.