I've had trouble with verb-tense agreement since day one of English learning.
According to a lot of native speakers who have addressed this subject on several English forums, when the tenses in a sentence aren't consistent, it will immediately sound weird to their ears. For instance, one ought to say
"I thought you couldn't take a picture here"
"I thought you can't take a picture here"
even when the prohibition of picture-taking is still in effect.
However, when I tried to say "I guess that..." or "I suspect that...," I wondered if I had to do the same. Then, I Googled a bit, and realized that with suspect/guess, tense agreement works differently. A lot of people say things like "I guess he didn't" and so on. Is it true that with verbs like guess and suspect, different grammar is involved? Am I mistaken?
I'd really appreciate it if someone would shed some light on this. Thank you.