"I do not think about it."
Translation:Nemyslím na to.
the simple answer is that it looks and sounds very foreign. unfortunately, going beyond simple gets tricky fast, as it ventures straight into one of the two most frustrating areas of czech grammar for foreign learners.
the issue is that outside of sentence-initial positions, the pronomial "to" (i.e., one used instead of a noun rather than with one) and its combinations with prepositions behave like weak enclitics. they want to sit in the second position in the clause, after the first unit of meaning. (they are weak because when more enclitics cluster up in that slot, they tend to go as the last ones.) maybe a few examples without clustering:
- Na to nemyslím. and Na to já nemyslím. and even Na to nemyslím já. are all ok because "na to" is not an obligatory enclitic. it can start a clause.
- Nemyslím na to. is ok, second position.
- Já na to nemyslím. ditto
- Já nemyslím na to. has "na to" in the third slot and that makes it sound really foreign. it is similar to Já nevidím ho.
czechs do not make this mistake, even if most of us can't explain what the mistake consists of. we are not taught about obligatory or weak enclitics in grade school, and most of us never learn what those might be. somehow we feel our way through it, get it through osmosis. (and here is where the course has two alternatives. start accepting the foreign word order just to avoid debating it over and over, or let the student fail repeatedly and eventually figure it out by feel.)
if you google "já nemyslím na to" in books, you will find hits, but they will all continue the sentence, often with a subordinate clause describing the "it" that i don't think about. this is done to avoid separating the subordinate clause from the "to" that it depends on.
- Já nemyslím na to, že padnu. (I am not thinking about being killed.)
- Já nemyslím na to, co by řekl můj kardiolog. (I don't think about what my cardiologist would say.)
Well, according to Google, there are people using that phrase: https://www.google.cz/search?client=ubuntuhs=DDrq=%22nemysl%C3%ADm+o+tom%22oq=%22nemysl%C3%ADm+o+tom%22gs_l=psy-ab.3...3102.4544.0.4718.104.22.168.0.0.0.177.293.0j2.2.0....0...1.1.64.psy-ab..0.0.0....0.UKTHaFV7zzc
However, it sounds odd to me too and I have never heard someone saying that.