Is there a way to mark questions in which I do not parcitipate as observed so when anything changes in observed topic I gen notified by inbox in top left corner?
Yes, you can - by clicking the little star to the left of the question, you mark it as a "favorite". More details are provided here.
The notifications it provides are displayed on the "StackExchange" logo on the upper left of the site.
However, it appears that the notifications are temporarily broken. When they come back online, marking a question as one of your "favorites" will do what you want.