How can i transfer Expenses already registered to bills?i notice under suppliers the expenses i mentioned paid wont shows negative on total.

Let me help you with your expenses, lamice_nassoura.

Bills and expenses on the Expenses tab will show a positive amounts under the Total column. When you pay the bill, the Bill Payment will show a negative amount. 

In addition to this, QuickBooks Online let's you record business expenses in three different ways. You'll use the Expense option if you've already paid for a business expense. You can create a bill if you plan to pay for the expense in the future. Or write a cheque if you make a purchase with a hand-written cheque or print a new one.

You can browse this article to help you select the specific transaction type of expense to use for your payables: Learn the difference between bills, cheques, and expenses in QuickBooks Online.

When it's time to review your transactions, the first thing to do is make sure your books are accurate. Make sure you’ve entered all your transactions into QuickBooks. Then, reconcile your accounts in QuickBooks so they match your real-life bank and credit card statements.

Get back to me if you need have additional questions about your bills and expenses. I'm always around to help you.