"It's dark there, that's why I think that he is going to fall."
Translation:Там темно, поэтому я думаю, что он упадёт.
Would считаю work as well ? I thought it meant "I guess" or "I reckon" or "estimate".
I'm native speaker and we actually don't see any great difference between "here" and "there" (тут\там). You can even see this fact in a dictionary)
And still there is a difference in the meaning (I'm a native Russian speaker too). «Тут» is something nearby, «там» is somewhere you can point your finger at. In fact, dictionaries list тут and там as antonyms, which is about as far apart as words can get. I don't understand what I am supposed to ”see” in a dictionary.
As a side note, you can use the report button to suggest translations.