Он шел. (шел - is mostly used for continuous tenses, but sometimes it is used for simple tenses).
Он шел по улице. – He was walking on the street.
Он шел к своей цели. – it may mean 1) He walked to his aim. or 2) He was walking to his aim.
As you know there are not any differences between simple and continuous tenses in Russian language.
Что ты будешь делать сегодня? It means: What will you do today? or What will you be doing today?
Что ты делал(а) сегодня? – What did you do today? or What were you be doing today?
But there are some verbs (like «идти», «ходить») in Russian which have different forms for using in “simple” or “continuous”. But they haven’t strong rules like in English.
Ехать, ездить; лететь, летать; плыть, плавать.
Good luck