What is the difference between отида/отивам and ходя ?Feel free to just provide example sentences.

Basically, "ходя" implies "to go" multiple times (or in multiple directions), while ""отида/отивам" implies only one time and in one direction. Moreover, the direction is specified as from "here" to "there". In order to imply the reverse direction (from "there" to "here"), we use other verbs like "дойда" "идвам", etc.
Ходя до магазина да пазарувам веднъж седмично. (multiple times, every week)
Отивам до магазина да пазарувам. (just now, "there" is the shop, and "here" is where you are, or where I am, or where my usual place, or home is)
Идвам от магазина след 5 минути. (just the oposite)

That's just in theory though, in practice the verbs of motion are not always used quite logically and often such uses can only be learned by heart.