Get down.
In Italian, 'scendi' is the imperative form of the verb 'scendere', which means 'to get down' or 'to go down'. It is used to instruct someone to descend from a higher place or to move downwards. For example, you might say 'Scendi le scale' to tell someone to 'Get down the stairs'.
Get off the bus
This phrase is an imperative command instructing someone to get off (scendi) the bus. In this context, 'dal' is a combination of the preposition 'da' and the article 'il', used before 'bus' to denote that the person is exiting from it.
When you go down the stairs, be careful
This is a cautionary statement advising someone to be careful (fai attenzione) while descending (scendi) the stairs (le scale). The conjunction 'quando' is used to indicate 'when' the action is occuring.
Go down to do the shopping
In this phrase, someone is being told to go down (scendi) to do the shopping (fare la spesa). The preposition 'a' is used after 'scendi' to indicate the purpose or direction of the action.