this is a thng which is super difficult to explaine because there is no exact rules on where to put the stress. i have looked all over and couldnt find a thing but this didnt keep me from learning russian. the best thing i would recomend is tring to guess where the stressed o is and most of the time it will be right. like Достопримечательности this is a long word which means sights and as you can see many o's are in this word.
now the thing is none of the o's are stressed here from what i have heard. but a russian would understand if you did stress any o in here.
as for spelling well this is a different story . just try to remember the words and i think you will be fine. if anyone wants to add anything or make any corrections to what i have said please feel free to
большой спасиба for yr reply that confused me more. I thought there should be a solid ground for the use of "o" but now i understand there isn t. so i guess by practising n making a lot of mistakes i ll manage if u did. thank u.
i looked up for eg in dictionary the long word u wrote n found out that all of the "o" s are read as ы. no rules then just memorization. i wont loose my courage.