Questions & Answers about Раньше они часто гуляли по берегу.
Why do we use the preposition по here instead of a word for 'on'?
In this lesson, you are learning that по followed by the Dative case often means 'along' or 'around' a surface. Using по берегу gives the feeling of moving along the shoreline or casually wandering around the beach.
Why does the word берег end in -у here?
The noun берег (shore or bank) is in the Dative case because it follows the preposition по. For masculine nouns that end in a hard consonant, you form the Dative case by adding an -у to the end.
Why is the imperfective verb гуляли used here instead of a perfective verb?
The words раньше (earlier or in the past) and часто (often) tell us this was a repeated habit. In Russian, repeated or habitual actions in the past always require the imperfective aspect.
Could I use a standard motion verb like ходили instead of гуляли?
You could, but it changes the nuance. The verb гулять specifically means to stroll, go for a leisurely walk, or hang out. Using a motion verb like ходить usually suggests you were walking with a specific destination or purpose in mind.