Translation:I thought that the lecture was going to be tomorrow.
Why isn't "I thought that the lecture is tomorrow" an acceptable answer.
In English it's very common to use the present simple for events in the near future.
For example: "I have a class today" (Present Simple) In Russian: «Сегодня у меня будет урок »
"I thought the lecture will be tomorrow" is a very unnatural English sentence and is a very common mistake made by Russian ESLs
It's because in English the tense has to match, and "thought" doesn't match "is". You have a couple ways to say this in English, either "thought" and "was going to be" (past tense thinking about the "future" from a past tense point of view), or "thought" and "would be" (past and subjunctive), but "thought" and "is" happens to not be proper English grammar.
Note that the answer you see depends on what you wrote yourself. The accepted answers allow quite a number of things that would be unnatural, were it the course of English rather than Russian—it is essentially the same as the quality of Russian in the course of English (to be honest: poor quality; some translations of particulalry tricky sentences barely makes sense at all).
mmm I have had this issue a number of times also. It isn't a problem so much when you can click on the outline because you can click again to put it back and then just work through the partially visible tabs. When there is a whole line and no visibility, that is different. I think I fixed it once by clicking on the 'use keyboard' tab and then switching back again. It appeared to readjust itself. You could try it and see if it works for you...
The present tense forms are думаю, думаешь, думает.... думают (same pattern as читать).
Only past tense forms end in -л, -ла, -ло or -ли. Actually, virtually all of them end this way with the exception of a few verbs that have a consonant before л; the consonant eats up the masculine suffix (e.g. the past form of "can": мог, могла, могло, могли)
It may be easier with another example.
Suppose there is a tall boy whose birthday is tomorrow:
Present: (I am thinking about him now)
I think the boy is tall.
I think the boy is going to smile.
I think the boy is going to smile tomorrow.
Past: (I was thinking about him yesterday.)
I thought the boy was tall.
I thought the boy was going to smile.
I thought the boy was going to smile tomorrow.