How to make my application faster

Question

Hello, I have a problem with my application is a little bit slow. It takes 1-2 sec to change panels. Below i describe how it works. Description: Main form with splitContainer. SpliContainer1 has a treeview. SplitContainer2 has PanelCustomer, PanelOrders. PanelCustomer retrieves data filtered by CustomerID from SQL Server and has insert/edit/delete actions. PanelOrders has two sections. At first it gets all orders for the selected customer (with their details) and it shows in TabControl the products for the particular order, some history and the warehouses of the products. It keeps opening and close connections to SQL Server. Any suggestions how to make it faster? ( i know it a general description) Thank you in advance.