Translation:They went to the park the next morning.
That is also not correct word order in English. Modifying adjectives always come before the noun, with very few exceptions.
"...the following morning" is perfectly good English and means the same thing.
how did u go in the future ? went is past and next morning is future. can some1 explain this?
Just last month they had spent a weekend in the city. The night they arrived, they saw a show. They went to the park the next morning.
they went to the park ON the next morning. isn't it correct? duolingo refused this version.
No. You can say "They went to the park on Thursday (etc.)", "They went to the park on the morning of the fourth of July (etc.)", and "They went to the park in the morning.", but you say "They went to the park the next morning". (without a preposition).