Leigh gave a good answer.
With regard to 'nature,' Russian speakers usually include the article 'the' when talking about nature, but you don't need to use an article for 'nature,' generally.
'I like to be out in nature.'
Sometimes 'the' will be used if it's in reference to a particular place's nature: 'The nature on Arizona is very beautiful.' But, if you're talking about nature in a general sense, you don't really need an article.
In the US, we tend to use the word 'hike' to differentiate between walking in the city/urban setting from walking in nature. So if you're walking in the woods, in the mountains, or in a rural area somewhere on a rough trail, we often say 'hike' or 'hiking.'
'I usually go hiking for exercise.'
'For exercise, I usually take a hike.'