Close or Reverse Position
To close or reverse 1 position, go to the contract screen of the position, click the + option > Close position or Reverse Position.
Also, on Open Positions screen, you can hold your finger on one of the positions on the list and a menu with these options will come up.

Cancel or Edit Order
To cancel 1 order, go to the contract screen of the position, and look for your order on Active Orders for that contract. You will see a Cancel icon and an Edit icon next to it.
Also, on Active Orders screen, you can hold your finger on one of the positions on the list and a menu with these options will come up.

Close All Positions
On the Main screen, look for the Orders tab. Here, click on Open Positions. You will find the Close All Positions option. After confirming you wish to Close All, a market order with inverse volume is sent for each position, except for Options, where the position remains unaltered.
If the positions are not closed, there could be a reason why the orders could not be filled, you can check them in rejected orders.

Cancel All Orders
On the Main screen, look for the Orders tab. Here, click on Active Orders. You will find the Cancel All option. After confirmation, all orders in the list will be cancelled.