Question

1. Don't talk to him now, he (thinks, is thinking) of something. ​

Answer 1

1. Don't talk to him now, he is thinking of something. ​

He thinks - он считает, что / он думает, что (по его мнению);

He is thinking - он думает, размышляет.

Answer 2

Both "thinks" and "is thinking" are grammatically correct options, but they slightly differ in meaning:

1. "Don't talk to him now, he thinks of something": This suggests that he regularly or habitually thinks of something, and the speaker is advising not to disturb him because he is likely to be engrossed in his thoughts.

2. "Don't talk to him now, he is thinking of something": This implies that he is currently in the process of thinking about something specific, and the speaker is advising not to interrupt him while he is actively engaged in his thoughts.

Both options convey a similar idea, so you can choose the one that best fits the context and the intended meaning of the sentence.