Diana, здесь настоящее время

Very good, Elena! "I guess" in English is the same as saying "obviously." Does полагаю have the same force in Russian?

да

Uly , it can be translated also as думаю, предполагаю, считаю, мне кажется ...

but the English doesn't mean думаю - that's a common mistake I've seen among Russians.

it's closer to наверняка, должно быть, and other expressions of certainty based on factual knowledge or clear evidence.

In Russian "полагаю" и "думаю" are synonyms
http://dic.academic.ru/dic.nsf/ushakov/954206
"Думаю" In Russian is not only "I think". That's the clue to some misunderstanding

Ещё, насколько я понимаю, "мне кажется" тоже не совсем подходит для "I guess". Это больше подходит для "I'm guessing". Uly, is that right?

That is correct. I don't know about Russian, but "I think" and "I guess" are not synonymous in English. One expresses uncertainty and the other a certainty based on physical or factual evidence (as in this post). The woman only says "I guess" because the man is shaking his head. Also I GUESS has an element of очевидно это просто так и все. So in this case, the fact that he's shaking his head leaves her no doubt that he doesn't understand. That's why you can't use it with any other person but the first person.

I don't know about Russian, but I think and I guess https://gas-stationsnearme.com/ are not synonymous in English. One expresses uncertainty and the other a certainty .