Direcly decrease bank (cash) money when order is bought?

sorry for bad english. When i have bought something i want to know if its possible to select a bank or cash account. if its possible how do i do this.

Yes, you can select an individual account. Read the Guides beginning at http://guides.manager.io/businesses/bank-accounts.

When you purchase are you paying cash or are you paying at a later date?.
If you are paying cash, just select your bank account then Spend Money.
If you are paying at a later date, use Purchase Invoice, then bank account Spend Money when paying.

Perhaps if the above doesn’t answer you question, you could provide more details?