સમય બગાડવો

It can be. Telling someone 'You are wasting time' is a direct criticism. Use it carefully with elders.

The opposite is 'Samay no sadupayog karvo' (To make good use of time).

No, for money we use 'Paisa bagāḍavā' or 'Paisa udāḍavā'.

Yes, 'Vakhat' is an older, more formal word for time, often used in the same phrase.

You would say 'Huṃ mārī jindagī bagāḍī rahyo chuṃ'.

Yes, to explain a gap year or a failed project, e.g., 'I didn't want to waste time, so I learned a new skill.'

Because 'Samay' is a masculine noun, and the past tense verb matches the object's gender.

Youth often say 'Veti thā' (Get lost) to someone who is wasting their time.

Usually, yes. It implies you could have done something better but chose not to.

No, you'd say the machine is 'slow' (dhīmuṃ). This phrase is for human actions.